In this report from a longitudinal study, the main aim was to evaluate the long-term predictive strength of a novel cartoon-based risk-taking trait assessment, which might prove to have utility in future research on mechanisms leading toward illegal drug involvement. The study population originated as 2311 first-graders entering 19 elementary schools during two successive school years. The assessments started soon after the children entered primary school. The key response variable was participants' use of cocaine by the time of a young adult assessment. We found that for each standard deviation increase in the risk-taking scale there was a two-fold increase in the risk of becoming a cocaine user by young adulthood (estimated relative risk, RR = 1.9; 95% confidence interval, CI = 1.3, 2.7). Independently, onset of cannabis use by young adulthood was also predicted by risk-taking scale values, but use of legal drugs (alcohol and tobacco) was not. These long-span associations provide support for new research on very early risk-taking mechanisms that lead toward illegal drug involvement. © 2008 Elsevier B.V. All rights reserved.