OBJECTIVES: Medicaid is the largest payer of HIV antiretrovirals (ARVs) in the US. To assess the trends in Medicaid utilization of ARVs and expenditures in the period 1991-2014, and to compare the utilization and reimbursement rates of generic and brand ARVs in the study period. METHODS: ARVs data were gathered from the Food and Drug Administration website. Utilization and expenditure data were collected from the Center for Medicare and Medicaid Services website. The unit of analysis was the defined daily dose (DDD). Descriptive analyses were performed to assess the Medicaid ARVs utilization, reimbursement rate, and average reimbursement per 30 DDD.  RESULTS: Utilization of HIV ARVs in Medicaid increased over the study period from 21,000 30 DDD in Q1-1991 to 930,000 30 DDD in Q2-2014.  Further, utilization of generic ARVs in Medicaid increased from 58 30 DDD in Q4 2004 to 93,000 30 DDD in Q2 2014. Likewise, Medicaid annual expenditures on ARVs increased from $5.2 million in Q1 1991 to $702 million in Q2 2014. During the study period, 7 ARVs out of 35 ARV products had generic competition in Medicaid program.  The market share of generic ARVs increased from 8.2% in the first quarter of their launch to 89.5% by the end of the 3^rd year after the generic entry into the market. The average Medicaid reimbursement rate for generics was 81% of the brand reimbursement rate at the first quarter of the generic launch, and decreased to 76% by the end of the 3^rdyear after generic market entry.  CONCLUSIONS: Several factors may explain Medicaid ARVs utilization and expenditures during the study period including the number and type (i.e. generics and brands) of FDA ARV approvals, the Medicaid generic drug utilization rate, changes in therapeutic guidelines, and states’  policies and regulations regarding Medicaid ARVs coverage and reimbursement mechanisms.