As shown by a study of drug addicts serving prison sentences in Southern Italy, the international drug trafficking system has had a strong impact on the general problem of drug addiction. Drug addiction is linked closely with organized crime, and as such it is responsible for diverse manifestations of social as well as individual pathology. Six case studies of drug-addicted prisoners illustrate the intensity of the problem of drug addiction among convicts and the potential beneficial effect of appropriate therapy on both physical and psychological addiction. Penal institutions are in an ideal position to screen for, diagnose, and treat addiction to alcohol, hashish, heroin, morphine, and other narcotic substances. The optimal multidisciplinary team should consist of the director of the institution, his social assistant, an expert in sociology, an educator, a neurologist, and a psychologist.