Many researchers have speculated about the role peer groups play in adolescent development, but few have examined teenagers' own perspective on the importance of group affiliations. The two studies reported here, involving 1,300 7th to 12th graders in three Midwestern U.S. communities, assessed teenagers' valuation of belonging to a "crowd" as well as the reasons they cited to support or oppose crowd affiliation. The importance of crowd affiliation declined across age. Younger adolescents generally favored membership, emphasizing the crowd's ability to provide emotional or instrumental support, foster friendships and facilitate social interaction. Older respondents expressed dissatisfaction with the conformity demands of crowds and felt their established friendship networks obviated the need for peer group ties. The importance of crowd affiliation was not related to the strength of respondents' sense of identity but did vary significantly with their willingness to conform to peers and the centrality of their position in peer groups or the type of crowd to which they belonged. Findings emphasized that adolescent peer groups can serve multiple functions, whose salience shifts with age.