Elevated levels of serum lipids and lipoproteins are known to play a major role in the development of atherosclerosis and subsequent coronary heart disease (CHD). In controlled clinical studies, atorvastatin (Sortis), a new 3-hydroxy-3-methyl-glutaryl-coenzyme-A (HMG-CoA)-reductase inhibitor, proved to be a very effective and safe lipid-lowering agent. The aim of this open-label, multicentre study (without a control group) was to confirm the efficacy and safety of atorvastatin in a private practice group, including 181 Swiss cardiologists, internists, and general practitioners. A total of 877 hyperlipidaemic patients requiring treatment participated in this study. To evaluate the effectiveness of the treatment with atorvastatin over a period of 12 weeks, total plasma cholesterol (TC), HDL cholesterol, LDL cholesterol and triglycerides (TG) were determined every 4 weeks. The initial atorvastatin dose was 10 mg in 78% of patients and 20 mg in 22%. The dose was doubled every 4 weeks until the target values of TC < or = 5.2 mmol/l and TC/HDL < or = 5 were reached. After 12 weeks of treatment with atorvastatin the mean reduction in TC, TC/HDL, LDL and TG compared to baseline levels was 33, 37, 42, and 25% respectively. At the same time the HDL concentration was increased by 9%. These results were evidenced in patients with existing coronary heart disease, in high risk patients without manifest coronary heart disease and in patients with significantly elevated lipid levels (TC > 7.8 mmol/l, TC/HDL > 6.5). After treatment with atorvastatin for 12 weeks, 59% of patients had reached the therapeutic target of TC < or = 5.2 mmol/l. The target of TC/HDL < or = 5 was reached by 79%. Atorvastatin was almost without exception well tolerated, the most frequently reported side effects being nausea, myalgia, and headache. In this open-label multicentre study atorvastatin was found to be effective and well tolerated. The observed reduction in the lipid and lipoprotein concentration is in accordance with the results of published controlled studies. The lipid and lipoprotein concentrations were decreased significantly in patients with slight to moderate elevation of lipid levels as well as in those with significantly raised values.