Several methodological limitations should be noted. First, the current study relied on self-reported STI information and no corroborative biological data were available. Given that asymptomatic STIs are prevalent and adolescent awareness of infection tends to be low (Kane et al. 2001), the rate of STIs in the current sample is likely to be underestimated. Second, we elected to combine girls reporting no sexual activity in the past year with girls who were sexually active but not engaging in risky behaviors. It is possible that this approach masked some developmental heterogeneity whereby some of these girls may have engaged in sexual risk behaviors at an earlier time, then desisted. However, data suggest that sexual risk-taking is relatively stable (e.g., 60% of girls in the current sample using birth control inconsistently at age 15 also reported inconsistent use at age 16, χ2=23.2, df=1, p<.001). Nevertheless, the approach of combining these possibly different types of girls into one group likely produced more conservative findings about the predictive utility of increasing alcohol use for subsequent sexual risk-taking than if prior sexual history was also
