Morbidity and mortality rates for regular heroin users are much greater than those observed in the general population. In 'high-risk' heroin users implantable naltrexone has been used under Commonwealth Therapeutic Goods Administration Compassionate guidelines in Western Australia since August 2000. This pilot study compared the frequeney of accidental opiate overdose and other morbidity resulting in hospital presentations in eight 'high-risk' dependent heroin using adolescents pre- and post-naltrexone implant treatment. We reviewed the hospital medical records retrospectively for the participants across the four public hospitals in Perth. The review period was September 1999-October 2002. The eight adolescents (aged 15 19 years) initially underwent naltrexone implant treatment between September 2000 and September 2001. The data indicated a dramatic reduction in opiate overdose post-implantable naltrexone treatment, with a smaller reduction in opiate overdose during oral naltrexone treatment compared to the pre-orallimplant period. Implant treatment in the high-risk heroin user may provide an important prophylaxis against mortality associated with accidental opiate overdose. These encouraging findings now require validation using a larger cohort over an extended period.