Most studies investigating the efficacy of naltrexone maintenance as a treatment for illicit heroin use have reported poor patient compliance in taking naltrexone. A number of studies have, however, reported better compliance when patients receive family therapy, or when patients resided in a supportive family environment. These studies suggest that patient outcomes on naltrexone maintenance may be better if there is ongoing family support to continue naltrexone use. The current study investigated 6-month outcome status in 300 illicit heroin users who commenced naltrexone maintenance in a community-based out-patient treatment programme. The study aimed to assess the relationship between vigilance of naltrexone supervision by salient others over the first 6 weeks of treatment and patient status at 6 months. Supervision of naltrexone at week 6 was a predictor of a patient's status at 6 months, with those receiving less supervision of 3–4 days more likely to have returned to heroin use or be assessed as ‘heroin use undetermined’. In contrast, patients who still received naltrexone supervision for 6 or 7 days per week at week 6 were more likely to be taking naltrexone or were naltrexone- and heroin-free at 6 months. It is argued that since relapse to heroin use is a common occurrence, vigilant supervision of naltrexone dosing in a supportive environment may improve patient retention and reduce relapse. It is suggested that poor outcomes reported in many previous studies may reflect use of inadequate supportive frameworks that encourage naltrexone compliance.