The first step in program modification is comprehension. Several researchers argue that programmers utilize plan-based representations when composing or comprehending code. In this study we tested the psychological validity of this proposal and examined the nature of plan-based program representations. Experienced programmers were asked to segment code and sort programs. The segmenting data showed that programmers agree on the major components of a program and that these components are defined by goals in a plan representation. Pascal and FORTRAN programs that employ the same plan structure were segmented into similar components. Program sorting data also showed clustering into plan groups. However task related dimensions are also important parts of program representations.