Several models of categorization assume that fixed perceptual features are combined together to determine categorization. This research explores the possibility that categorization experience alters, rather than simply uses, featural descriptions of objects. In the first part of the reported experiments, subjects learned to categorize objects on the basis of particular sets of line segments. In the second part, subjects were given a perceptual part/whole judgment task (Palmer, 1977). Categorization training influenced subjects' part/whole judgments, indicating that whole objects were more likely to be broken down into features that were diagnostic during categorization. The results indicate an influence of subjects' ewerience on the segmentation of objects into parts. The results are discussed in terms of perceptual sensitivity, response bias, and how they are modulated by experience.