In a prospective study of 282 chronic alcoholics and 67 opiate addicts, frequency and pattern of drug intake were determined by questioning and urinalysis on admission to a special unit of a psychiatric hospital. 20.2% of alcoholics and 44.8% of opiate addicts stated that they had taken psychotropic drugs before admission, women in both groups naming such drugs significantly more frequently than men. But taking into account results of urinalysis, 25.5% of alcoholics and 31.3% of opiate addicts were found to have taken benzodiazepines before hospital admission. 41.8% of opiate addicts either stated or were found to have taken barbiturates. High dosages of benzodiazepines were found in those alcoholics who had mentioned taking them. Thus in practice the treatment of addicts differs markedly from recommendations made by well-known experts. There is also a need to improve the clinical diagnosis and treatment of addicts.