Exhibit 15.1 Letter Re: Unaudited Interim Financial Information June 27, 1996 Board of Directors and Shareholders' CUC International Inc. We are aware of the incorporation by reference in the Proxy Statement of Ideon Group, Inc. that is made a part of the Registration Statement (Form S-4) and Prospectus of CUC International Inc. for the registration of 17,170,469 shares of its common stock of our report dated May 22, 1996 relating to the unaudited condensed consolidated interim financial statements of CUC International Inc. that are included in its Forms 10-Q for the quarter ended April 30, 1996. Pursuant to Rule 436(c) of the Securities Act of 1933 our reports are not a part of the registration statement prepared or certified by accountants within the meaning of Section 7 or 11 of the Securities Act of 1933. /s/ Ernst & Young LLP ERNST & YOUNG LLP Stamford, Connecticut