Background Anti-illicit-drug public-service announcements (PSAs) have become a cornerstone of drug policy in the USA. However, studies of the effectiveness of these interventions have not been subjected to a systematic evaluation. Methods The authors searched 10 electronic databases along with major conference abstract databases (from inception until 15 February 2010) for all articles and abstracts that evaluated the effectiveness of anti-illicit-drug PSAs. The authors evaluated all studies that assessed intention to use illicit drugs and/or levels of illicit-drug use after exposure to PSAs, and conducted meta-analyses of these studies. Results The authors identified seven randomised trials (n=5428) and four observational trials (n=17 404). Only one randomised trial showed a statistically significant benefit of PSAs on intention to use illicit drugs, and two found evidence that PSAs significantly increased intention to use drugs. A meta-analysis of eligible randomised trials demonstrated no significant effect. Observational studies showed evidence of both harmful and beneficial effects. Conclusion Existing evidence suggests that the dissemination of anti-illicit-drug PSAs may have a limited impact on the intention to use illicit drugs or the patterns of illicit-drug use among target populations.