OBJECTIVE: Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure V (1993) and VI (1997) recommend diuretics and beta-blockers as initial antihypertensive drugs. However, a few studies have shown a trend of increasing use of angiotensin-converting enzyme inhibitors (ACEIs) and calcium channel blockers (CCBs), and decreasing use of diuretics and beta-blockers. The purpose of the study was to examine the impact of insurance types on patterns of antihypertensive drug use. METHODS: A logistic regression model was employed to examine whether insurance type was associated with patterns of antihypertensive drug use by using Medical Expenditure Panel Survey (MEPS, 1996), after controlling for confounding variables. The estimated study population enrolled was 10,357,769 non-institutionalized adult US patients with essential hypertension. RESULTS: Patients with HMO insurance were less likely to use diuretics or beta-blockers (OR=0.499, 95%CI: 0.323-0.770), compared with the patients with fee-for-service (FFS) insurance. Black patients were less likely to use diuretics or beta-blockers compared with white patients (OR=0.577, 95%CI: 0.346-0.961). Compared with non-married patients, married patients were 92 percent more likely to use diuretics or beta-blockers (OR=1.92, 95%CI: 1.299-2.838). Finally, patients diagnosed between 1988 and 1992, and after 1993 were less likely to use diuretics or beta-blockers (OR=0.486, 95%CI: 0.289-0.817; OR=0.416, 95%CI: 0.251-0.691), compared with patients who were diagnosed with hypertension before 1988. CONCLUSION: Insurance types are associated with the patterns of antihypertensive drug use. Patients with HMO insurance used more ACEIs or CCBs than patients with FFS insurance. Further research is required to discern the reasons for the impact of insurance types so that policy makers can propose efficient intervention.