Kelley-Quon LI, et al. - Through an 8-wave prospective longitudinal cohort study of 14- and 15-year-old high school students (n=3,298) in Los Angeles, CA who had never consumed heroin at baseline, researchers evaluated if nonmedical prescription opioid use was correlated with ensuing heroin use in adolescents. The mean per-wave prevalence of prior nonmedical prescription opioid use was 1.9% and of current nonmedical prescription opioid use was 2.7% from waves 1 to 7. A total of 70 students began heroin use during waves 2 to 8. Prior vs no and current vs no nonmedical prescription opioid use was positively correlated with start of consequent heroin use. The calculated cumulative probabilities of ensuing heroin use initiation by wave 8 were 1.7%, 10.7%, and 13.1% for no, prior, and current nonmedical prescription opioid use statuses at waves 1 to 7, respectively. Correlations were reduced in covariate-adjusted models, however, they stayed statistically significant and current nonmedical prescription opioid use risk estimates were more powerful than corresponding correlations of nonopioid substance use with subsequent heroin use initiation. Among Los Angeles youth, nonmedical prescription opioid use was prospectively correlated with subsequent heroin use initiation throughout 4 years of adolescence.