This study will be a retrospective observational study assessing identifiable tolerability problems in terms of their comparative incidence among Human Immunodeficiency Virus (HIV) patients treated with cART regimens including one of four different protease inhibitors [Atazanavir sulfate (ATV), Darunavir (DRV), Fosamprenavir (FPV), or Lopinavir (LPV)] and the impact of these identifiable tolerability problems on PI persistence, healthcare utilization, and healthcare costs.

Inclusion Criteria:

• Initiated treatment with a Protease inhibitor (PI)-based Combination antiretroviral therapy (cART) regimen
• Between 18-64 years of age on the index date
• At least 6 months of continuous enrollment and pharmacy benefits prior to the index date
• At least 6 months of continuous enrollment and pharmacy benefits following the index date
• At least 1 medical claim during the 6-month follow-up period

Employees and dependents with employer-based health insurance coverage