This study investigates the association linking truancy and drug-related experiences among adolescents sun,eyed via a street outreach program. A total of 2126 adolescents aged 12 to 18 years recruited from Taipei street sites completed a self-administered anonymous questionnaire. The lifetime prevalence of illicit drug use for adolescents with truancy was 15.0-17.9% (12.1-14.5% for ecstasy, 4.6-7.3% for ketamine, and 3.5-8.8% for marijuana), and the corresponding estimate was 3.1-3.4% for youths without truancy. Multiple logistic regression analyses showed a dose-response effect linking the maximum days of truancy with illicit drug us. After holding constant of psychosocial environmental factors and use of readily available substance (i.e., alcohol, tobacco, and betel nut), the results of survival analyses suggested that there might be reciprocal relationships operating between illicit drug use and truancy. These findings may help form programs to identify or monitor youths at risk.