This paper explores the recent explosion in university patenting as a source of insight into the changing relationship between the university and the private sector. Before the mid-1980s, university patents were more highly cited, and were cited by more diverse patents, than a random sample of all patents. More recently several significant shifts in university patenting behavior have led to the disappearance of this difference. Thus our results suggest that between 1965 and 1988 the rate of increase of important patents from universities was much less than their overall rate of increase of patenting.