This case describes a heroin addict who was participating in a placebo-controlled randomized trial of naltrexone as an aid to relapse prevention. The patient tried to commit suicide by taking a heroin overdose after learning that he was HIV-positive. He was on naltrexone at the time and, as a result, survived what would probably have been a fatal overdose. This case demonstrates that naltrexone can have immediate as well as long-term positive effects in persons who are attempting to recover from heroin addiction.