OBJECTIVES: Angiotensin-converting-enzyme inhibitors (ACEIs) are used by millions of Americans to treat high blood pressure, heart failure, and kidney disease. The objective of this study was to analyze the drug price trends of ACEIs, and to assess drug utilization and market-share competition in US Medicaid Programs. METHODS: The monthly average wholesale price (AWP) per daily antihypertensive dose for each ACEI was evaluated using data extracted from the First DataBank. Data for ACEIs available between 1989 and 2002 were assessed. National Medicaid pharmacy data files were also analyzed to construct the quarterly prescription numbers and per-prescription reimbursement figures for each drug from 1991 through 2004. The market-share of ACEIs was calculated based on proportion of numbers of prescriptions. RESULTS: The average AWP per daily antihypertensive dose for brand-name drugs increased over time, while the AWP for generically available ACEIs decreased dramatically after being introduced into the market. The AWP per daily dose for Prinivil, Vasotec, Zestril were approximately $2 to $2.50 and relatively higher than other ACEIs. The average reimbursement per prescription for brand-name ACEIs in Medicaid increased from $33.30 in 1991 to $49.30 in 2004. The average reimbursement per ACEI generic prescription in Medicaid decreased from $34.00 in 1996 to $24.60 in 2004. The market share of brand-name ACEI prescriptions dropped from 100% in 1991 to 20% in 2004. After generic ACEIs became available, brand-name prescriptions decreased dramatically. The generic market share took over the brand-name market share in 2003 due to the increasing use of lisinopril and enalapril. CONCLUSIONS: Generically available ACEI AWP and reimbursement prices decreased due to competition, but there was little impact on brand-name reimbursement prices. The market share competition between brand-name and generic drugs was observed in Medicaid programs. Decreased use of brand-name ACEIs might be due to Medicaid policy of generic substitution when available.