Friendship factors have been implicated in adolescent suicidality, but this relationship has not been verified across ethnicities. This study examined suicidality and friendship problems (i.e., social isolation, poor friendship quality, friends' school disconnection, and friends' delinquency) among Mexican American adolescents, an understudied, vulnerable group in terms of suicidality. Three hundred thirty-eight community adolescents, two-thirds of whom were educationally at-risk, participated in the study. Suicidal ideation and behavior rates were high, particularly among girls. Friends' school disconnectedness increased girls' odds for suicidal ideation by 13%. This association was even greater for girls in good academic standing. Friendship problems were not associated with suicidality in boys. Ethnic identity was a minor factor in suicidal ideation, and only for girls. These findings confirm, among Mexican American adolescents, the role of gender in the relationship between friendship and suicidality. (Contains 2 tables.)