This paper illustrates an approach to hybrid architectural form-making. A hypothetical project - the Des Moines Art Center 3rd Addition - is employed as a design experiment. The computer is used as a form-searching medium in the form-making process. Suggesting an addition to the existing center designed by Saarinen, Pei, and Meier, the designer is confronting the problem of how to respond to the three distinct architectural styles. The proposed solution to this problem is to create a hybrid building which inherits architectural properties from those precedents. Potentials of the use of the computer for such task are discussed.