Cognitive processing in autism has been characterized by a difficulty with the abstraction of information across multiple stimuli or situations and subsequent generalization to new stimuli or situations. This apparent difficulty leads to the suggestion that prototype formation, a process of creating a mental summary representation of multiple experienced stimuli that go together in a category, may be impaired in autism. Adults with high functioning autism and a typically developing comparison group matched on age and IQ completed a random dot pattern categorization task. Participants with autism demonstrated intact prototype formation in all four ways it was operationally defined, and this performance was not significantly different from that of control participants. However, participants with autism categorized dot patterns that were more highly distorted from the category prototypes less accurately than did control participants. These findings suggest, at least within the constraints of the random dot pattern task, that although prototype formation may not be impaired in autism, difficulties may exist with the generalization of what has been learned about a category to novel stimuli, particularly as they become less similar to the category's prototype.