This paper describes a multi-institutional study that used categorization exercises (known as constrained card sorts) to investigate gender differences in graduating computer science students' learning and perceptions of programming concepts. Our results show that female subjects had significantly less pre-college programming experience than their male counterparts. However, for both males and females, we found no correlation between previous experience and success in the major, as measured by computer science grade point average at graduation. Data also indicated that, by the time students completed their introductory courses, females reported nearly equal levels of mastery as males of the programming concepts. Furthermore, females generally considered the programming concepts to be no more difficult than did the men.