for the first illicit drug use, 14 years for drug abuse with dependence, and 15 years for drug abuse without dependence. Similar to the pattern in alcohol use, there was a slight overall male preponderance in prevalence of stages of drug use, which was most pronounced among older adolescents. The same pattern of racial/ethnic differences was observed across the 3 age cohorts, with black and other racial/ethnic groups having typically lower rates than white or Hispanic adolescents. High rates of opportunity to use drugs and drug use were observed among Hispanic adolescents, especially in the youngest age cohort. Concerning conditional prevalence rates, 40.5% of the sample used illicit drugs when given the opportunity, and more than one-third of adolescents who used illicit drugs developed abuse (36.6%). The overall patterns of effects by sex and race/ethnicity in the conditional prevalence rates for drug use stages were highly similar to those observed for alcohol, as demonstrated by increasing male preponderance in transitions among older adolescents and generally lower rates of transitions, particularly among black adolescents. Concerning types of illicit drugs, cannabis was the most frequently used substance in all age cohorts (Table 3). The use of each category of illicit substance was
