Objective: To describe the changes in costs of care for HIV-positive patients in Italy after the spread of antiretroviral combination therapies (HAART). Methods: Five thousand four hundred and twenty-two patients from the I.CO.N.A. (Italian Cohort Naive Antiretrovirals) study were followed between 1997 and 2002. Costs included antiretroviral therapies (ART), hospital admissions, prophylaxis, and main laboratory examinations. The perspective was that of the National Health Service. M. Merito et al. / Health Policy 74 (2005) 304-313 305 Conclusions: From 1997 to 2002 inpatient costs progressively decreased in favor of antiretroviral therapy. Annual average costs per patient decreased, while total direct costs increased over time: health resources, initially concentrated on hospitalized patients were then distributed over a growing number of subjects.