Surveys on drugs and alcohol availability show that (1) alcohol is much more easily accessible than both cannabis and tobacco, and that (2) many adolescents still do not find it ‘easy’ to access those substances. In the current study, we examine the importance of both opportunity and availability in assessing substance use in adolescence. Our measures of opportunity include skipping school and unstructured socializing, while availability measures include parental substance use and perceived availability of tobacco, alcohol, and cannabis at home. We draw from two waves of the National Longitudinal Study of Adolescent to Adult Health (Add Health) survey, and distinguish between (a) predictors of Wave II substance use for the whole sample, and (b) predictors of Wave II initiation for those respondents who reported no use at Wave I. We find that availability at home and parental substance use is correlated with substance-specific current adolescent consumption, but these indicators are not associated with initiation behavior. Instead, initiation seems to be carried by unstructured socializing outside of the home, with availability at home acting as reinforcement once some level of substance use is established.