OBJECTIVE To describe and understand current care of simvastatin-treated patients with combined hyperlipidemia in routine clinical practice. METHODS A 6-month prospective observational study. Demographics, simvastatin dosage, cardiac risk factors, and lipid profile were collected from August 1997 to December 1998 at 20 sites (230 patients) across the United States. RESULTS Overall mean percentage of reduction in total cholesterol levels was 27% (P<.001), low-density lipoprotein cholesterol (LDL-C) was 35% (P<.001), and triglyceride values was 28% (P<.001). Among those patients with low baseline high-density lipoprotein cholesterol (HDL-C) values (<0.91 mmol/L [<35 mg/dL]) (N = 49), there was a 17% increase in HDL-C (P< or =.001); 35% of these patients achieved National Cholesterol Education Program HDL-C goal (ie, < or =0.91 mmol/L [> or =35 mg/dL]). Coronary heart disease (CHD) patients were given significantly higher initial doses (mean, 15.1 mg) compared with non-CHD patients (mean, 11.5 mg) (P< or =.001). Overall, 74% of patients achieved LDL-C goal (52% on starting dose, 22% after 1 titration). Among those patients who were not at goal and had a follow-up lipid profile result available, only 1 patient (2%) was at the maximum dose (80 mg); 69% were receiving 20 mg or less. Approximately 63% of patients with CHD, 80% of patients with 2 or more risk factors, and 91% of patients with fewer than 2 risk factors achieved LDL-C goal. CONCLUSIONS Multiple factors contribute to LDL-C goal achievement in a usual care setting. A significant opportunity exists to increase the number of patients who achieve LDL-C goal by appropriate dose titration and/or give patients a higher initial dose of simvastatin.