Without good compliance the best psychiatric treatment is ineffective. This article reviews what is known or can be inferred about compliance with psychiatric medications in the pediatric population. The review includes discussions of assessment techniques, risk and protective factors, the relevant research literature, and research-based practical techniques to improve compliance. A Medline search surveying the years from 1966 to August 2000 yielded only seven peer-reviewed papers reporting on compliance with pediatric psychopharmacology. All seven studies looked at stimulant compliance among children with attention deficit hyperactivity disorder. Reported levels of compliance range from 56% to 75%. These rates, although low, are likely to be overestimates of actual compliance. We review two related areas of research for which there are small but significant bodies of knowledge: pharmacological compliance studies among adult psychiatric populations and pediatric medical populations. This literature supports the idea that medication compliance is a significant obstacle to the effective treatment of patients. Because compliance rates are lower for children as compared to adults and psychiatric patients as compared to medical patients, we suspect that children with psychiatric illness may be at great risk for poor medication compliance. Fortunately, the research literature demonstrates several simple techniques that clinicians can use to improve medication compliance among their patients. The treatment alliance; education; and medication duration, dosing, palatability, and cost can all be tailored to improve medication compliance.