Few studies investigating the effectiveness of methadone treatment for opiate dependence have emanated from the UK. The core feature of treatment offered by Lothian Health's Community Drug Problems Service involves the prescribing of methadone by the client's general practitioner. Of a cohort of 494 daily users of opiates attending the service, 39% remained in treatment for at least 12 months. Up to 2 years in-treatment follow-up revealed significant improvement in injecting and criminal behaviour. There were no HIV seroconversions reported during the treatment period. There was no improvement in injection equipment sharing, condom use, illicit drug use or employment status. 'Satisfactory' discharge was achieved for 40% of those in treatment for at least 6 months. These results are largely consistent with the outcomes of methadone programmes elsewhere.