We estimated the AIDS survival by neighborhood socioeconomic status before (1993-1995) and after (1996-1997) the introduction of highly active antiretroviral therapy in Rome, Italy, in a retrospective cohort of persons with AIDS followed through July 31, 1998. Participants included 1,474 persons with AIDS residing in Rome who were diagnosed in 1993-1997. We calculated hazard ratios (HRs) of death for two diagnostic periods (before and after highly active antiretroviral therapy was introduced) by neighborhood socioeconomic status categorized into four levels (level I = highest socioeconomic status), using the Cox model and adjusting for gender, age, intravenous drug use, CD4 cell count at diagnosis, AIDS-defining disease, and hospital of diagnosis. Thirty-four per cent of persons with AIDS (N = 503) had survived as of mid-1998. For persons with AIDS diagnosed in 1993-1995, we found little difference in the risk of death by neighborhood socioeconomic status. For 1996-1997, the risk of death was greater for persons with lower neighborhood socioeconomic status, especially for levels III and IV [HR = 2.81 (95% confidence interval = 1.38-5.76), and HR = 2.55 (95% confidence interval = 1.27-5.14), respectively, compared with level I]. Stratified analyses showed that the greatest difference was found for women and drug users. In conclusion, even in a country with universal health coverage that provides therapy at no cost, differences in survival of persons with AIDS have emerged by neighborhood socioeconomic status since highly active antiretroviral therapy was introduced. Inequalities in health-care access or in medical management, or poor adherence to treatment, could explain the observed heterogeneity.