This article examines the role of friends in girls' and boys' advanced course taking and explores whether friends' characteristics are particularly important for girls' math and science attainment. With the use of data from Adolescent Health and Academic Achievement and the National Longitudinal Study of Adolescent Heath, the results indicate that same-sex friends' academic performance significantly predicts course taking in all subjects for girls, but not for boys. Furthermore, for math and science only, the effects of friends' performance are greater in the context of a predominantly female friendship group, which suggests that such groups provide a counterpoint to the gendered stereotypes and identities of those subjects.