The aim of the study was to analyze the impact of soci-economic status in addition to other risk factors in the progression of HIV disease in a cohort of injecting drug users (IDUs) with a mean follow-up of two years. Between 1989 and 1992, 124 HIV-infected IDUs were recruited in a primary care outpatient clinic providing free consultations and free access to therapy. The main outcome measures were death and AIDs-defining events. The proportion of current daily injectors at entry in the study and at the end of follow-up was 67.7% and 57.2%, respectively. The proportion of individuals on maintenance opioid therapy at entry in the study and at the end of follow-up was 0 and 12.1%, respectively. CD4 cell counts below 200 x 10(6)/L at baseline, positive p24 antigenemia at baseline, the lack of legal income and occasional drug use at entry were risk factors for clinical progression and death. When adjusted in a multivariate analysis, the absence of legal income remained associated with death and occurrence of an AIDS-defining event with a relative risk of 5.2 (1.5-18.1) (p = 0.004). Lack of legal income is a strong risk factor for progression of HIV disease in IDUs, that is independent of CD4 cell count and p24 antigenemia.