Background: There is currently evidence that methadone and buprenorphine maintenance is effective in reducing substance abuse. However, it is not known whether psychosocial support improves the outcome of methadone maintenance in the absence of control measures, such as regular urine testing. Materials and Methods: In a prospective observational study, the effectiveness of standard psychosocial support [SPS] was compared with enhanced psychosocial support [EPS]. EPS included intensive case management and drop-in centres. Subjects were administered the Addiction Severity Index before and after treatment and were followed up at 18 months post-treatment, and case files were reviewed. No subjects in either SPS or EPS condition were subjected to a substantial amount of control measures such as urine testing. Results: Clients in EPS support received more treatment according to case-files, and showed a lower proportion of no-shows compared with those receiving SPS. Subjects in both SPS and EPS reduced drug use and legal problems, but enhanced care was more effective at reducing social problems, family problems and psychiatric severity. Mortality was slightly, although non-significantly higher in the control group. Change in psychiatric and social problems were associated with the absence of no-shows. Discussion: Enhanced psychosocial support appeared to be effective at reducing problems associated with drug use in a low-threshold buprenorphine or methadone maintenance setting without substantial measures of control.