Aim: To determine the rate of current major depressive disorder (MDD) among entrants to treatment for heroin dependence in three treatment modalities and a non-treatment comparison group; and to ascertain factors associated with depression. Design: Cross sectional structured interview. Setting: Sydney, Australia. Participants: 615 current heroin users: 201 entering methadone/buprenorphine maintenance (NIT), 201 entering detoxification (DTX), 133 entering drug free residential rehabilitation (RR) and 80 not in treatment (NT). Findings: Current major depressive episode was reported by 25%. The rates of major depressive disorder ranged from 26% in the treatment groups (23% NIT, 25% DTX, 31% RR) to 16% of those not in treatment. Females were more likely to have current major depressive episode (31% versus 21% OR 1.70, 95% Cl 1.16-2.48). Factors associated with depression in the treatment groups were post traumatic stress disorder (PTSD), attempted suicide in the last 12 months and severe physical disability. Among the non-treatment group those with depression were also more likely to have PTSD. Women entering treatment were three times more likely to meet criteria for current major depression than women not in treatment. Among men however, the rates were not significantly different. Conclusion: Depression is a significant concern among entrants to treatment for heroin dependence. An essential component of treatment should be a consideration of depression, with the provision of appropriate treatment were required. (c) 2004 Elsevier Ireland Ltd. All rights reserved.