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                                                                       Exhibit 5

                      [Letterhead of Debevoise & Plimpton]

August 24, 2001


Landstar System, Inc.
13410 Sutton Park Drive South
Jacksonville. Florida 32224

Dear Sirs:

         We have acted as counsel to Landstar System, Inc., a Delaware
corporation (the "Company"), in connection with the filing by the Company of a
Registration Statement on Form S-8 (the "Registration Statement") relating to
500,000 shares of the Company's Common Stock, par value $.01 per share (the
"Common Stock"), to be issued upon exercise of options granted pursuant to the
Landstar System, Inc. 1993 Stock Option Plan (the "Plan").

         We have examined the originals, or copies certified or otherwise
identified to our satisfaction, of the Plan and such other corporate records,
documents, certificates or other instruments as in our judgment are necessary or
appropriate to enable us to render the opinion set forth below.

         Based on the foregoing, we are of the opinion that authorized but not
previously issued shares of Common Stock which may be issued upon exercise of
options granted under the Plan have been duly authorized and when issued in
accordance with the terms of the Plan will be validly issued, fully paid and
non-assessable.

         We hereby consent to the filing of this opinion as an exhibit to the
Company's Registration Statement. In giving such consent, we do not thereby
admit that we are within the category of persons whose consent is required under
Section 7 of the Securities Act of 1933 or the rules and regulations of the
Securities and Exchange Commission thereunder.

                                            Very truly yours,

                                            /s/ Debevoise & Plimpton