A community-based sample of 412 low-birth-weight and 305 normal-birth-weight children and their mothers were initially assessed when the children were 6 years old, with a follow-up assessment at age 11. Neuropsychological performance, child psychiatric disorders, and behavior problems were measured at age 6 and age 11. Children's self-reports of drug use, parent monitoring, and peer drug use were obtained at age 11 only. Mothers' history of psychiatric disorder was measured with the Diagnostic Interview Schedule when the children were 6 years old. Findings show that the relationship of ADHD with drug use varied by level of externalizing problems. Regardless of ADHD status, children with a low level of externalizing problems had a low risk of drug use, and those with the highest level of externalizing problems had a high risk. At the middle level of externalizing problems, ADHD increased the incidence of drug use to the magnitude observed at the high level of externalizing problems, and children with ADHD were at significantly higher risk than those without ADHD (odds ratio = 2.1, p = .03). Findings were similar for low-birth-weight and normal-birth-weight children. Low parent monitoring and high peer drug use signaled increased risk of drug use for children, independent of ADHD status. Psychostimulant treatment for ADHD was unrelated to risk of drug use. The authors conclude that risk for early drug use in children with ADHD depends on the level of associated externalizing problems. Parent monitoring and peer drug use are apparently potential targets for drug prevention for children with ADHD, as well as children in general. 2 tables, 3 figures, and 52 references