Mental health (MH) hospital admissions were investigated in a cohort (N 1184) of heroin dependent persons using linked health records. All MH in-patient admissions were extracted 36 months before to 36 months after commencing rapid opioid detoxification ( ROD) and oral naltrexone. Results show that the incidence rate ratio (IRR) of drug-related and other MH admissions peaked in the 3 months immediately prior to treatment. All categories subsequently declined to baseline levels by 36 months following treatment. The authors conclude that treatment for heroin dependence reduces risk of MH admissions.