This study evaluated the effects of a community-based drug use prevention program on the frequency with which doormen at licensed premises intervene in cases of obviously drug use-impaired patrons. Doormen were trained in recognizing signs of drug use impairment to be able to stop drug use-impaired patrons to enter the premises. The study included 28 trendy nightclubs in Stockholm, Sweden, that used doormen to screen patrons. Two male actors were instructed to act as if they were obviously drug use-impaired (cocaine/amphetamines) while attempting to enter nightclubs. Data were collected at pretest when 40 entry attempts were made (2003) and posttest (2004) when 48 attempts were made. At follow-up, the doormen intervened in 27% of the attempts, a significant improvement compared to the intervention rate of 7.5% at baseline. The results indicate that the intervention has had effect on doormen's behavior. However, in the majority of the attempted visits, the doormen still did not intervene. Limitations of the study were the lack of a control group and problems with identifying the training status for the individual doormen. Further research is necessary to explore the effectiveness of community-based drug use prevention programs targeting licensed premises.