Numerous antiretroviral therapy (ART) regimens are recommended for first-line and subsequent HIV care, but regimen selection for clinical use may not represent the full range of options. We hypothesized that despite an increase in available antiretrovirals, clinical trial data on regimen efficacy and fixed-dose combination options have lead to uniformity in initial ART. We evaluated regimen selection for ART-naïve patients at the University of Alabama at Birmingham (UAB) 1917 Clinic between January 2000 and December 2007. The annual number of unique initial regimens was quantified. Initial regimen variability was expressed as regimens per 100 patients. Subsequent ART regimens were characterized for complexity via regimen sequence trees detailing the first three generations of regimens for patients starting the two most common initial combinations. Four hundred eighty-two ART-naïve patients were treated with 39 unique initial regimens (8.0 regimens per 100 patients). Variability in initial regimen selection was highest in the first 6 years (14.9-24.4 regimens per 100 patients). A sharp decline was observed in 2006 (16.1 regimens per 100 patients) and 2007 (6.5 regimens per 100 patients). The most dramatic shift in drug selection involved an increase in emtricitabine plus tenofovir plus efavirenz, from 0% in 2003 to 85% in 2007. During the study period, 205 of 482 (43%) patients required a change in initial therapy. Of these, 156 of 205 (76%) had a unique sequence of regimens. A shift toward homogeneity of initial ART was observed (85% of patients received the same first-line regimen in 2007). In contrast, regimen sequencing beyond the first regimen remained complex. These shifts in ART prescribing patterns may have implications for collaborative HIV care. © 2010, Mary Ann Liebert, Inc.