the high-risk sample (0.85). We labeled this class “preadolescent multiproblem” as it was defined by preadolescent initiation of sexual activity, tobacco use, and alcohol/drug use. The second risk class represented 14 % of the sample. Boys in this class had a high probability of being early (but not very early) sexual initiators (1.00), early (but not very early) tobacco initiators (0.70), and early (but not very early) alcohol users (0.64). Relative to the other classes, these boys also had a somewhat elevated probability of causing pregnancy (0.35) but were not likely to contract a STD (0.03). Urban African American boys had an elevated probability of being in this class (0.27) relative to urban or rural European American boys (0.00 and 0.02, respectively), as did youth in the high-risk sample (0.86). We labeled this class “adolescent multi-problem” to reflect the initiation of tri-morbid problems during mid-adolescence (grades 9–10). Boys in class 3 (approximately 30 % of the sample) had a high probability of very early tobacco initiation (0.87) and very early alcohol initiation (0.59), but were likely to delay sexual initiation (0.54), with a corresponding low probability of causing pregnancy or contracting a STD (0.06–0.01, respectively). Urban and rural European American
