RULE 424(B)(3)
                                                              FILE NO. 333-62081
 
                  PROSPECTUS SUPPLEMENT DATED OCTOBER 19, 1998
              TO PROXY STATEMENT/PROSPECTUS DATED OCTOBER 1, 1998
 
    This document supplements the information in the Proxy Statement/Prospectus
sent to stockholders of IMNET Systems, Inc. in connection with the stockholders
meeting scheduled for October 30, 1998 to vote on the merger of IMNET with a
subsidiary of HBO & Company.
 
    On October 17, 1998, HBOC entered into an agreement providing for the
acquisition of HBOC by McKesson Corporation in a merger. The merger agreement
provides that each HBOC stockholder will receive 0.37 shares of McKeeson stock
for each share of HBOC stock. The merger is subject to regulatory approval and
approval by the stockholders of HBOC and McKesson, as well as other customary
conditions. The merger is expected to close in the first quarter of 1999.
McKesson stock is listed on The New York Stock Exchange under the symbol "MCK."