HIV infection is a disease that can not be eradicted which, if left untreated, leads to AIDS and death from an opportunistic infection. Antiretroviral drugs stop viral replication thus preventing disease progression. Due to the fast emergence of drug resistance if used in monotherapy, regimes containing three drugs are most common. Two drugs in the regime are NRTI, which make the nucleoside backbone, and the other is either NNRTI, PI, or II. The aim of this research was to determine if there are differences in frequency and reasons for change of the first line antiretroviral therapy taking into consideration sociodemographic factors (age, sex, residence, probable route of transmission), factors that indicate severity of the disease (viral load, CD4 cell count, AIDS), and the ART combination and nucleoside backbone. The studied population is treatment naive patients who started ART between 2012 and 2016 in Croatia. The main outcome was ART change which was defined as either switch or discontinuation with the follow-up period being 1 year after the start of ART or until the first change. Out of 508 subjects 181 (36.5%) of them had a change in initial ART. Statistical analysis included survival analysis, and Cox regression with models for the whole time of follow-up, the first 30 days of follow-up, and all days past the first 30. The results show that ART regimes containing II had less risk of change compared to other regimes. The most significant correlation with the risk of change was found for regimes that contained ZDV3TC as a nucleoside backbone (p < 0.001). These results support new guidelines that reccomend II based regimes as first line therapy and no longer recommend ZDV as a part of the initial ART.