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                                                                     EXHIBIT 5.1
 
                                              December 9, 1996
 
Primark Corporation
1000 Winter Street
Suite 4300N
Waltham, Massachusetts 02154
 
Ladies and Gentlemen:
 
     Reference is made to the Registration Statement on Form S-8 ("Registration
Statement") of Primark Corporation (the "Corporation") related to the
registration of 1,414,276 shares of the Corporation's common stock, without par
value ("Common Stock"), which are to be offered or sold pursuant to the TASC
Profit Sharing and Stock Ownership Plan (the "Plan").
 
     I have been requested to furnish an opinion to be included as Exhibit 5.1
to the Registration Statement. In conjunction with the furnishing of this
opinion, I have examined such corporate documents and have made such
investigation of matters of fact and law as I have deemed necessary to render
this opinion.
 
     Based upon such examination and investigation, and upon the assumption that
there will be no material changes in the documents examined and matters
investigated, I am of the opinion that the 1,414,276 shares of Common Stock
referred to above have been duly authorized by the Corporation and that, when
issued in accordance with the terms of the Plan, will be legally issued, fully
paid and nonassessable.
 
     I consent to the filing of this opinion as Exhibit 5.1 to the Registration
Statement.
 
                                             Very truly yours,
 
                                             /s/ MICHAEL R. KARGULA
                                             ----------------------------- 
                                             Michael R. Kargula, Esq.
                                             Senior Vice President,
                                             General Counsel and Secretary