OBJECTIVE: To compare the effects of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) with non-statins on compliance duration, healthcare utilization, and healthcare costs in an Health Maintenance Organization (HMO) population. METHODS: A retrospective cohort study was performed using claims data and survey data in continuously enrolled patients (n=810) with prescriptions for antihyperlipidemic medications from 04/1993 to 03/1995. Compliance duration was defined as the duration of over 80% compliance with antihyperlipidemic medications, healthcare utilization measures as hospital admissions due to cardiac diseases and outpatient visits, and healthcare cost variables as total healthcare costs, net costs, and drug cost. Each main outcome measure was modeled (Tobit model for compliance duration, probit model for healthcare utilization, and OLS model for healthcare costs). RESULTS: The statins significantly prolonged the compliance duration (p<0.05). The factors significantly influencing on compliance duration were female gender, baseline high compliance, chronic disease scores, number of cholesterol-lowering drugs in the regimen, and diagnostic characteristics such as peripheral vascular diseases (PVD), cardiac diseases (CVD), hypertension and diabetes. The statins significantly decreased adjusted hospital admissions due to CVD in year 1 (p<0.05) especially in those patients with PVD (p<0.01) and CVD (p<0.05). There was no significant difference in total healthcare costs in year 1 between patients on statins and those on non-statins. However, in year 2 and pooled data (year 1 and year 2), the statins were significantly associated with higher total healthcare costs (p<0.05, p-pooled<0.05) and higher drug costs (p<0.0001, p-pooled<0.0001). CONCLUSIONS: The statins improved patient’s compliance of antihyperlipidemic therapy. The statins also decreased the hospital admissions due to CVD without significantly elevated healthcare costs in the short term (year 1).