EXHIBIT (d)(6)

                                                                    May 24, 2002


Cemex, Inc.
Avenida Constitucion 444
PTE. 6400 Monterrey, N.L., Mexico

Attention:        Mr. Philippe Gastone
                  Senior Vice President

Dear Mr. Gastone:

     UBS Warburg, LLC ("UBSW") is acting as financial advisor to Puerto Rican
Cement Company, Inc., a Puerto Rico corporation ("PRCC"), in connection with a
possible transaction involving PRCC and Cemex, Inc. ("Cemex") by way of merger,
sale of assets or stock, or otherwise (the "Proposed Transaction"). Each of PRCC
and Cemex may furnish certain confidential nonpublic information to each other
in order to assist the other party in making an evaluation of the Proposed
Transaction. Each party hereto, in consideration of the other party's agreement
to furnish information to it (each party furnishing such information shall be
hereinafter referred to, with respect to such information, as the "Disclosing
Party" and each party receiving such information shall be hereinafter referred
to, with respect to such information, as the "Receiving Party"), agrees, as set
forth below, to treat any information whether so provided before or after the
date of this Confidentiality Agreement (this "Agreement") in connection with the
Proposed Transaction, whether such information is written or oral or otherwise
recorded, and whether or not such information is specifically identified as
"confidential," that is learned in connection with visits to the Disclosing
Party's facilities or otherwise communicated or furnished to a Receiving Party
by a Disclosing Party or on behalf of a Disclosing Party by a Representative (as
hereinafter defined) (such information being herein collectively referred to as
the "Evaluation Material") in accordance with the provisions of this Agreement
and to take or abstain from taking certain other actions herein set forth.

     The term "person" as used in this Agreement shall be broadly interpreted to
include the media and any other corporation, partnership, group, individual or
other entity.

     The term "Evaluation Material" shall also include all analyses,
compilations, forecasts, studies or other material prepared by a Receiving Party
or any of its affiliates, directors, officers, employees or subsidiaries, or any
person identified on Schedule A hereto or such additional persons as to which
prior notice of such person's identity is given to the other party hereto
(collectively, the "Representatives") containing, based on or reflecting any
confidential non-public information furnished by a Disclosing Party or any of
its Representatives. Notwithstanding the foregoing, the term "Evaluation
Material" shall not include information that (i) is or becomes generally
available to the public, other than as a result of a disclosure by a Receiving
Party or any of its Representatives in violation of this Agreement, or (ii) is
already or becomes available to a Receiving Party from a source other than the
Disclosing Party or its Representatives, provided that such source is not known
by such Receiving Party to be in breach of a confidentiality agreement with or
other obligation of secrecy to the Disclosing Party or a third person.

     Each Receiving Party hereby agrees to use the Evaluation Material solely
for the purpose of evaluating the Proposed Transaction involving the parties
hereto and agrees to keep such information confidential, to treat it with the
same degree of care it uses in protecting its own confidential and proprietary
data, not to use it in any way detrimental to the Disclosing Party and not to
disclose it, directly or indirectly, in any manner



whatsoever; provided, however, that (i) any of such information may be
disclosed by a Receiving Party to those of its Representatives who need to know
such information for the purpose of evaluating the Proposed Transaction
involving the parties hereto (it being understood that such Representatives
shall be informed of the confidential nature of such information and shall be
directed to treat such information confidentially), (ii) any disclosure of such
information may be made if a Disclosing Party consents previously in writing,
and (iii) any disclosure of such information may be made as otherwise required
by law in the written opinion of counsel to the Receiving Party (including,
without limitation, pursuant to any federal or state securities laws or pursuant
to any legal, regulatory or legislative proceeding) or as contemplated by the
following sentence (the "Legal Exception"). In the event that a Receiving Party
or any of its Representatives receives a request to disclose all or any part of
the information contained in such Evaluation Material under the terms of a valid
and effective subpoena, order, civil investigative demand or similar process or
other written request issued by a court of competent jurisdiction or by a
federal, state or local, foreign or domestic, governmental or regulatory body or
agency, such Receiving Party agrees to the extent practicable to (A) promptly
notify the Disclosing Party of the existence, terms and circumstances
surrounding such request, (B) consult with the Disclosing Party on the
advisability of taking legally available steps to resist or narrow such request,
and (C) only disclose the information requested after complying with clauses (A)
and (B) and exercising reasonable effort (if so requested by the Disclosing
Party and at the Disclosing Party's sole expense) to obtain, to the extent
practicable, an order or other reliable assurance that confidential treatment
will be accorded to such portion of any disclosed information as the Disclosing
Party may designate.

     Each Receiving Party hereby assumes responsibility for all damages
resulting from any breach of this Agreement by any of its Representatives or
former Representatives. Each Receiving Party also agrees to take all reasonable
measures to restrain its Representatives or former Representatives from
prohibited or unauthorized disclosure or use of the Evaluation Materials. Each
Receiving Party hereby acknowledges that it is aware, and that it will advise
its Representatives who are informed as to the matters that are the subject of
this Agreement, that the United States securities laws prohibit any person who
has received from an issuer material, non-public information concerning the
matters which are the subject of this Agreement from purchasing or selling
securities of such issuer or from communicating such information to any other
person under circumstances in which it is reasonably foreseeable that such
person is likely to purchase or sell such securities. In addition, except (i)
with the prior written consent of the other party hereto or (ii) as required or
permitted under the Legal Exception, each party hereto will not, and will direct
its Representatives not to, disclose to any person either (A) the existence of
this Agreement or that the Evaluation Material has been made available to it, or
(B) in the event that the parties hereto engage in discussions or negotiations
with each other or their Representatives, the fact that discussions or
negotiations are taking place concerning the Proposed Transaction between the
parties hereto or any of the terms, conditions or other facts with respect to
any such Proposed Transaction, including the status thereof. If and to the
extent it is in the written opinion of counsel to a Receiving Party necessary or
advisable in litigation to support or defend actions taken by such Receiving
Party which are being reviewed or challenged in such proceedings, such Receiving
Party may disclose in such proceedings the matters described in the preceding
sentence and its analyses, compilations, forecasts, studies and other materials
relating to the Proposed Transaction that were prepared by such Receiving Party
and its Representatives. Each Receiving Party agrees to give the Disclosing
Party advance notice of any such disclosures to the extent practicable under the
circumstances.

         In consideration of being furnished the Evaluation Material and in view
of the fact that the Evaluation Material consists of confidential and non-public
information, each party hereto agrees that, for a period of 18



months from the date of this Agreement, it and its affiliates and associates (as
defined in Rule l2b-2 of the General Rules and Regulations under the Securities
Exchange Act of 1934, as amended) shall not, directly or indirectly, without the
prior written consent of the Board of Directors of the other party hereto, (i)
in any manner acquire, agree to acquire or make any proposal to acquire any
securities or property of such other party or any of its subsidiaries, (ii)
make, or in any way participate, directly or indirectly, in any "solicitation"
of "proxies" (as such terms are used in the proxy rules of the Securities and
Exchange Commission) to vote, or seek to advise or influence any person with
respect to the voting of, any voting securities of such other party or any of
its subsidiaries, (iii) form, join or in any way participate in a "group"
(within the meaning of Section 13(d)(3) of the Securities Exchange Act of 1934,
as amended) with respect to any voting securities of such other party or any of
its subsidiaries, (iv) otherwise act, alone or in concert with others, to seek
to control or influence the management, Board of Directors or policies of such
other party, (v) disclose any intention, plan or arrangement inconsistent with
the foregoing, or (vi) advise, assist or encourage any other persons in
connection with any of the foregoing. Notwithstanding the foregoing, it is
agreed that the foregoing restrictions will not prevent the Receiving Party's
investment bank from (i) engaging in brokerage, discretionary money management,
corporate finance, arbitrage and trading activities in the normal and usual
course of its business, (ii) acting on behalf of a person who engages in any of
the activities specified above in response to an unsolicited attempt by the
Receiving Party or any of its affiliates to acquire stock or assets of such
person, (iii) after the expiration of one year from the date hereof, acting on
behalf of a person unaffiliated with the Receiving Party who engages in any of
the activities specified above and (iv) arranging financing for any person
(other than a person on whose behalf it may not act pursuant to clause (iii)
above); provided that in each case set forth in clauses (i) through (iv) above,
none of the partners, officers or directors or employees of the Receiving
Party's investment bank involved in such representation shall utilize any
material non-public information that was derived from the Evaluation Material.
Each party hereto also agrees, for the period set forth in the last sentence of
this paragraph, not to (a) request the other party hereto or any of its
Representatives, directly or indirectly, that it be released from any provision
of this paragraph (including this sentence) or (b) take any action which might
require such other party to make a public announcement regarding the possibility
of a business combination or merger. If at any time during the period set forth
in the last sentence of this paragraph, either party is approached by any third
party concerning such party's or the third party's participation in any of the
activities described in clauses (i), (ii), (iii) or (iv) above, such party shall
inform such third party that such party is bound by certain confidentiality
obligations (without referring to this Agreement) and promptly inform the other
party of the nature of such contact and the parties thereto. Notwithstanding the
foregoing, nothing contained in this Agreement shall prevent one party hereto
from acquiring, or offering to acquire, any securities or assets of the other
party (the "Other Party") at any time after (i) the announcement or commencement
of a tender or exchange offer by an unrelated third party which, if consummated,
would give it ownership or control of 20% of more of the Other Party's
outstanding voting securities or (ii) the announcement by the Other Party that
it (or its Board of Directors) has agreed (including and agreement in principle)
to an acquisition of the Other Party or a substantial portion of its assets by a
third party or a merger or other business combination involving the Other Party
and a third party or a recapitalization or financial restructuring of the Other
Party. The agreements set forth in this paragraph shall terminate 18 months from
the date of this Agreement.

     In the event the Parties do not enter into the Proposed Transaction, Cemex
agrees that for one year from the date of the signing of this Agreement, it
shall not to solicit for employment or employ any of the current employees of
PRCC to whom Cemex had been directly or indirectly introduced or otherwise had
contact with or of whom Cemex became aware as a




result of its consideration of the Proposed Transaction with PRCC so long as
they currently are employed by PRCC and for three months thereafter, or solicit
any current suppliers, customers, or clients of PRCC, during the period in which
there are discussions conducted pursuant hereto and for a period of one year
thereafter, without the prior written consent of PRCC; provided, however, that
nothing in this paragraph shall be deemed to prohibit Cemex from (a) hiring
employees of PRCC who contact Cemex on their own initiative or due to any
solicitation by Cemex for employment by means of general advertising not
specifically directed at employees of PRCC or (b) soliciting suppliers,
customers, clients, or accounts of PRCC in the ordinary course of Cemex's
business consistent with past practice or in connection with Cemex's past or
current relationship with PRCC or any of its subsidiaries or affiliates
(provided that Cemex does not discuss the Proposed Transaction, or discuss or
share any Evaluation Material, with any such suppliers, customers, clients, or
accounts).

     Although each Disclosing Party has endeavored or will endeavor to include
in the Evaluation Material information known to it which it believes to be
relevant for the purpose of the Receiving Party's investigation, each Receiving
Party understands that neither the Disclosing Party nor any of its
Representatives has made or makes any representation or warranty either express
or implied as to the accuracy or completeness of the Evaluation Material. Each
Receiving Party agrees that neither the Disclosing Party nor any of its
Representatives shall have any liability to the Receiving Party or any of its
Representatives resulting from the use of the Evaluation Material.

     All Evaluation Material disclosed by PRCC is and shall remain the property
of PRCC. All Evaluation Material disclosed by CEMEX is and shall remain the
property of CEMEX. Each Receiving Party agrees to redeliver or cause to be
redelivered promptly to the Disclosing Party upon request (and in no event later
than five business days after such request) all written or otherwise tangible
Evaluation Material provided to it by the Disclosing Party or its
Representatives and not to retain any copies, extracts or other reproductions,
in whole or in part, of such written or otherwise tangible material. All other
Evaluation Material and documents, memoranda, notes, other writings and
otherwise tangible materials whatsoever prepared by a Receiving Party or its
Representatives based, in whole or in part, on the information in the Evaluation
Material which were not provided to the Receiving Party or its Representatives
shall be destroyed, and such destruction shall be certified in writing to the
Disclosing Party by an authorized officer of the Receiving Party who shall have
supervised such destruction.

         Each party hereto acknowledges and agrees that money damages would not
be a sufficient remedy for any breach by it of this Agreement, that the other
party hereto shall be entitled to equitable relief (including, without
limitation, and without posting security, injunction and specific performance)
as a remedy for any such breach or threatened breach, and that it shall not
oppose the granting of any such relief to such other party. Such remedy shall
not be deemed to be the exclusive remedy for a breach of this Agreement but
shall be in addition to all other remedies available to a party hereto for all
damages, costs and expenses (including reasonable attorneys' fees) incurred by
it in this regard.

         Each party hereto agrees that unless and until a definitive agreement
with respect to the Proposed Transaction has been executed and delivered,
neither it nor the other party hereto will be under any legal obligation of any
kind whatsoever with respect to the Proposed Transaction or any other similar
such transaction by virtue of this Agreement or any written or oral expression
with respect to such a transaction by any of its Representatives or by any
Representatives thereof except, in the case of this Agreement, for the matters
specifically agreed to herein.

         In the event that discussions between PRCC and Cemex are terminated by
either party for any reason whatsoever or for no reason prior to the



execution and delivery of a definitive agreement with respect to the Proposed
Transaction, Cemex agrees to pay all reasonable out-of-pocket costs, fees and
expenses incurred, directly or indirectly, by PRCC or its Representatives in
connection with the Proposed Transaction, including without limitation banking
and legal fees and expenses; provided, however, that Cemex shall not be
obligated to pay such costs, fees and expenses to PRCC if the discussions
between PRCC and Cemex are terminated by PRCC so that PRCC can negotiate a
similar transaction with another party.

     This Agreement (except for the standstill paragraph above, which is not
subject to modification, waiver or release) may be modified, waived or released
only by a separate writing by the parties hereto expressly so modifying, waiving
or releasing this Agreement. Each party hereto acknowledges and agrees that no
failure or delay by the other party hereto in exercising any right, power or
privilege hereunder shall operate as a waiver thereof, nor shall any single or
partial exercise thereof preclude any other further exercise thereof or the
exercise of any right, power or privilege hereunder.

     This Agreement is for the benefit of each of PRCC and Cemex and shall be
binding upon each others' successors in interest and assigns and shall inure to
the benefit of, and be enforceable by, each others' successors in interest and
assigns. This Agreement contains the sole and entire agreement between the
parties with respect to the subject matter hereof.

     If any provision of this Agreement is held by a court of competent
jurisdiction to be invalid, illegal or unenforceable, the remainder of the
provisions of this Agreement shall remain in full force and effect. The parties
hereto shall endeavor in good faith negotiations to replace any invalid, illegal
or unenforceable provision with a valid, legal and enforceable provision, the
effect of which comes as close as possible to that of the invalid, illegal or
unenforceable provision.

     This Agreement may be executed in one or more counterparts, each of which
shall be deemed to be an original but all of which shall constitute the same
agreement.

     This Agreement shall be governed and construed in accordance with the laws
of the State of New York applicable to contracts made, executed, delivered and
performed wholly within the State of New York without regard to the conflicts of
laws principles thereof. Each party hereto hereby (i) submits to the
jurisdiction of any state or federal court sitting in New York with respect to
matters arising out of or relating hereto, (ii) agrees that all claims with
respect to such matters may be heard and determined in an action or proceeding
in such state or federal court and in no other court, (iii) waives the defense
of an inconvenient forum, and (iv) agrees that a final judgment in any such
action or proceeding will be conclusive and may be enforced in other
jurisdictions by suit on the judgment or in any other manner provided by law.

     Please confirm that the foregoing is in accordance with your understanding
of our agreement by having a duly authorized officer of Cemex sign and return to
us a copy of this letter, whereupon this letter shall become a binding agreement
between the parties to this Agreement.

                                              Very truly yours,

                                              UBS Warburg LLC, on behalf of
                                              Puerto Rican Cement Company, Inc.


                                              By:  /s/ DAVID M. DICKSON JR.
                                                   -----------------------------
                                                   Name: David M. Dickson Jr.
                                                   Title: Managing Director



                                              Accepted and agreed to as of the
                                              date set forth above:

                                              Cemex, Inc.


                                              By:  /s/ JILL SIMEONE
                                                   -----------------------------
                                                   Name: Jill Simeone
                                                   Title: General Counsel




                                   SCHEDULE A

Representatives of Puerto Rican Cement Company, Inc.

         LeBoeuf, Lamb, Greene & MacRae, L.L.P.
         Parra, Del Valle, Frau & Limeres
         PricewaterhouseCoopers, LLP
         Totti & Rodriguez Diaz
         UBS Warburg LLC

Representatives of Cemex, Inc.

         Skadden, Arps, Slate Meagher & Flom, LLP
         Goldman Sachs
         KPMG