Continuous uninterrupted opiate substitution treatment for heroin users is the best predictor of drug-free discharge, a UK primary care-based study has shown. The prospective longitudinal cohort study was set in a GPwSI-led community drug service in Sheffield. Of 128 eligible patients entering treatment for opiate dependence in 1999, 123 were interviewed at baseline, with follow-up at one, five and 11 years. The Opiate Treatment Index was used as the primary assessment tool, and has outcome domains including drug use, BBV risk-taking behaviour, social functioning, criminal behaviour, health status and psychological wellbeing.