HIV-positive drug users are at high risk of HIV infection and are the target group of many HIV/AIDS prevetion and treatment programs in Vietnam. This paper aims to describe some socio-demographic characteristics and drug use history of HIV-positive drug users participating in the Methadone Maintenance Therapy (MMT) program in Hai Phong and Ho Chi Minh cities. The results showed that, at the beginning of treatment, the average age of patients was 30, 67 percent unmarried, had lower levels of education and 40 percent were employed. The duration of drug use before entering MMT was 9,2 years, 43 percent patients in Ho Chi Minh city and 16 percent patients in Hai Phong had shared needles and syringes with injecting partners when injecting drugs. Strengthening social support services for MMT patients including vocational training and jobs creationare recommended.