We report treatment protocols for HIV+/AIDS patients by CD4+ counts (T-lymphocyte cells/mm3: > or = 500, 499-200, 199-50, and < 50) as a tool to provide better definition and to project annual costs (total charges for services) and lifetimes costs for HIV+/AIDS. The treatment protocols, derived from the literature and an HIV+/AIDS Physician Panel, defined the resource use associated with antiretroviral therapy and opportunistic disease prophylaxis and treatment. Resource use costs were derived from the published literature, insurance database, Medicare fee schedules, surveys, and the Physician Panel. At CD4+ counts, the rates of opportunistic diseases were derived from the Physician Panel experience; the mean occupancy times were derived from the literature. The sensitivity analysis indicated stability of the lifetime costs to variation in mean occupancy times, rates of opportunistic diseases, rates of adverse events (AE), and costs. The total annual costs (1995 dollars) of HIV+/AIDS patients ranged from $1,934 (> or = 500), $6,015 (200-499), and $9,031 (50-199), to $25,239 ( < 50). The annual costs of opportunistic diseases are esophageal candidiasis (EC) ($2,194), tuberculosis (TB) ($2,924), cryptococcal meningitis (CM) ($17,264), toxoplasmosis ($17,631), Mycobacterium avium complex (MAC) (+20,153), Non-Hodgkin's lymphoma (NHL) ($22,329), wasting syndrome ($26,676), central nervous system (CNS) lymphoma ($27,333), Pneumocystis carinii pneumonia (PCP) [mild ($3,545), moderate ($4,889), and severe ($32,609)], Kaposi' sarcoma (KS) [mild/moderate ($5,902), and severe ($10,744)], and cytomegalovirus (CMV) retinitis ($100,337). The projected lifetime costs of HIV+/AIDS are $94,726 (annual costs $7,645). Our lower lifetime costs as compared with recent estimates may be due to including resources only for HIV+/AIDS-related treatment and not for non-HIV+/AIDS conditions, as well as reduced resource use resulting from more efficient diagnostic and therapeutic techniques and earlier prophylaxis provided by experienced HIV+/AIDS physicians. Nonetheless, our estimates are consistent with decreasing costs of HIV+/AIDS due to a reduction in the average length of stay and frequency of hospitalizations as well as to replacement of inpatient care by outpatient services.