Aims. To study the efficacy of standard hepatitis B (HB) vaccination in methadone-maintained former intravenous drug users. Design. HB vaccine was administered to subjects at 0, 1 and 6 months. Setting. Two university-affiliated methadone maintenance clinics. Participants. Forty-three HB-unexposed former heroin addicts in methadone maintenance treatment for heroin addiction. Measurements. HB surface antibody (anti-HBs) response to the vaccine was assessed at 0, 1, 6 and 12 months; anti-HIV-1 status was also assessed. Findings. Thirty-seven patients (86%) completed the 6-month vaccination series. Of the 30 anti-HIV-1 seronegative patients who then completed the entire 12-month protocol, 21 (70%) seroconverted (anti-HBs ratio 2.1) and 19 (63%) were protected (anti-HBs ratio 10). Two other subjects were anti-HIV-1 seropositive: one was HB-protected at 12 months but later lost immunity. Ten anti-hepatitis C antibody-positive patients completed the 12-month study and six were protected; thus, there was no significant relationship between hepatitis C status and HB vaccine response. Conclusions. Standard HB vaccination is both feasible and effective.