questionnaire. In-School Questionnaires were completed by more than 90,000 adolescents, representing a participation rate of approximately 80% of all enrolled students at the sampled schools. Add Health uniquely suits our research interests because respondents were asked to nominate up to five male and five female friends, from either the in-school roster or from among their out-of-school friends. If the friend was on the roster and also completed the questionnaire, we can identify characteristics of these friends such as race, ethnicity, gender, and all other items on the questionnaire. For this paper we use information on first-listed same-sex friends. 3 We do this for two reasons. First, Hartup (1993) found that only 5% of cross-sex friendships are not romantic. Second, Add Health instructions given to the respondents about friendship nominations asked them to include romantic relationships. Since romantic relationships operate in very distinct ways, we chose to use a strict definition of friendship (i.e. first-listed same-sex friend). If the first-listed friend was not on the roster (that is, they did not attend the school) or they were absent from school on that day, then we were unable to find their racial/ethnic information. In these cases, we turned to the second-listed friend. If the respondent did not choose first or second friend or both were not in the school roster, this adolescent does not have an assigned best friend. Over 55% of the respondents chose an identifiable best same-sex friend. Table 1 summarizes the measures we use in this study. Because respondents