This study was designed to test the effects of human potential seminar / grouptherapy on the mental health status and the knowledge of drugs among juvenile delinquents The grouptherapy included watching videos and lecture on drugs, personal unfoldment, peak experience, speaking of past experiences of alcoholism and misbehaviors, acknowledging personal strengths, recognizing those situation producing anger, remembering those who have loved participants planning for behavioral modification, making a time capsule, and candle ceremony. This study adapted one - group pretest and posttest design. Thirty-two subjects were obtained from a mental health program for adolescents. The grouptherapy was administered by a researcher and two assistants, who were qualified as mental health nurses. It was carried out 50 hours for 5 days and follow-up programs. These subjects joined both the main and the follow-up programs between November, 1994 and March, 1996. These programs wee to those adolescents with behavioral problems for rehabilitation referred from probation office. Questionnaires developed by Kim,s were used for the knowledge of drugs and Symptom Check List-90-Revision developed by Derogatis & Rock was used for mental health status. The data were analyzed by percent and paired t-test. The results were as follows ; 1. The changes of mental health following treatment were measured by SCL-90-R. All scores of somatization, obsessive-compulsive, interpersonal sensitivity, depression, anxiety, hostility, phobic anxiety, paranoid ideation, and psychocitism decreased significantly after treatment at 0.05 level. 2. As the knowledge of drug scores about narcotics, hallucinogens, stimulants, sedatives, minor tranqulizer, inhalants, alcohol, nicotine and ligality before and after treatment, the other except alcohol and nicotine increased significantly after treatment at 0.01 level. These results indicate that drug education and human potential seminar / grouptherapy is effective in increasing the knowledge of drugs, and improving mental health for juvenile delinquents and suggest that grouptherapy could be an effective nursing intervention method for juvenile delinquency in community.