STUDIES HAVE INDICATED THAT MANY ADOLESCENTS, ESPECIALLY DELINQUENTS, USE DRUGS. RESEARCH HAS YIELDED CONFLICTING ANSWERS TO THE PROBLEM OF BRAIN DAMAGE CAUSED BY DRUGS. SOME RESEARCH FOUND NO DAMAGE, SOME FOUND GENERALIZED DAMAGE, AND SOME SPECIFIC DAMAGE. MANY EXPERIMENTS ON THE EFFECTS OF ONE DRUG HAVE BEEN COMPROMISED BECAUSE OF FAILURE TO CONTROL FOR OTHER DRUGS OR MEDICATIONS. A SELECTION OF STUDIES ON THE RELATIONSHIP BETWEEN DRUG USE AND BRAIN FUNCTIONING ARE PRESENTED FOR HEROIN, ALCOHOL, MARIJUANA, HALLUCINOGENS, PHENCYCLIDINE, GLUE SNIFFING, NICOTINE, CAFFEINE, AND LEGAL MEDICATIONS. DRUG ABUSE CAN BE DETECTED THROUGH INTERVIEW TECHNIQUES, OBSERVATION, URINALYSIS, OR MEDICAL SYMPTOMS. PSYCHODYMANIC AND INTELLIGENCE TESTS HAVE ALSO BEEN CONDUCTED ON DRUG USERS, BUT WITH VARYING RESULTS. NEUROPSYCHOLOGICAL TESTS, PARTICULARLY THE HALSTEAD-REITAN BATTERY, SHOW CONSIDERABLE PROMISE AS DIAGNOSTIC METHODS. FUTURE AREAS FOR ANALYSIS OF DAMAGE POTENTIAL INCLUDE SPECIAL SENSITIVITIES SUCH AS PREGNANCY, REHABILITATION RATES, EFFECTS ON SPECIFIC BRAIN AREAS, AND ETHNIC DIFFERENCES. DRUG USE HAS ALSO BEEN RELATED TO CHARACTER DISORDERS, HEAD INJURIES, SERIOUS ILLNESS, AND DEPRESSION. REHABILITATION COULD BE MORE SUCCESSFUL IF THERAPY STARTED AFTER A DRYING-OUT PERIOD. THE TRIALS TEST HAS BEEN USEFUL IN MONITORING RECOVERY PROGRESS. HOWEVER DELINQUENT ADOLESCENTS POSE SPECIAL TESTING PROBLEMS BECAUSE OF THEIR SHORT ATTENTION SPANS AND POOR READING SKILLS. REFERENCES ARE PROVIDED. (MJM)