Purpose The purpose of this study is to estimate the average cost of treatment and investigate the related parameters of HIV/AIDS among patients based on their annual treatment regime during the 2017 in Izmir. Design/methodology/approach The average annual direct cost of an HIV patient's treatment was estimated for 2017 at four university hospitals in a retrospective study in Izmir, Turkey. Inclusion criteria included confirmed HIV infection, age = 18 years, visited one of the hospitals at least three times a year and with at least one CD4+ T cell count. The average annual treatment cost per patient was calculated using accounting data for 527 patients from the hospitals' electronic databases. Findings The mean treatment cost per patient was US$4,381.93. Costs for treatment and care were statistically significantly higher (US$5,970.55) for patients with CD4+ T cell counts of fewer than 200 cells/mm(3) than for other patients with CD4+ T cell counts above 200 cells/mm(3). The mean treatment cost for patients who were 50 years old or older (US$4,904.24) was statistically significantly higher than for those younger than 50 years (US$4,216.10). The mean treatment cost for female patients (US$4,624.92) was higher than that of male patients ($US4,339.72), although the difference was not statistically significant. The main cost driver was antiretroviral treatment (US$3,852.38 per patient), accounting for almost 88% of all costs. However, the high burden of antiretroviral treatment cost is counterbalanced by relatively low care and hospitalization costs in Turkey. Originality/value The paper contributes to the literature by providing average annual treatment cost of an HIV-infected patient in Turkey by using a comprehensive bottom up approach. Moreover, cost drivers of HIV treatment are investigated.