We used electronic name tags to conduct a fine-grained analysis of the pattern of socializing dynamics at a mixer attended by about 100 business people, to examine whether individuals in such minimally structured social events can initiate new and different contacts, despite the tendency to interact with those they already know or who are similar to them. The results show that guests did not mix as much as might be expected in terms of making new contacts. They were much more likely to encounter their pre-mixer friends, even though they overwhelmingly stated before the event that their goal was to meet new people. At the same time, guests did mix in the sense of encountering others who were different from themselves in terms of sex, race, education, and job. There was no evidence of homophily (attraction to similar others) in the average encounter, although it did operate for some guests at some points in the mixer. Results also revealed a phenomenon that we call “associative homophily,” in which guests were more likely to join and continue engagement with a group as long as it contained at least one other person of the same race as them. We consider the implications of these results for organizations and individuals seeking to develop their networks and for theories of network dynamics.