Aim To investigate the effect of the new potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, atorvastatin, on platelet aggregation in Chinese patients with hypercholesterolaemia. Methods Four agonists to induce platelet aggregation in whole blood were tested in normal subjects. The platelets showed good response to collagen in vitro but poor response to adenosine diphosphate (ADP) and adrenaline. The aggregation response to collagen 1.0 and 2.5 mg/L was assessed in 30 patients who had been receiving atorvastatin for 16 weeks, titrated at 4-week intervals through 10, 20, 40 and 80 mg daily until target low density lipoprotein cholesterol (LDLC) levels were achieved. Results The tests were repeated 4-weeks after stopping therapy. Withdrawal of atorvastatin resulted in the expected increases (all p<0.001) in total cholesterol (TC), triglycerides (TG) and LDLC from 5.0±1.1, 2.2±3.3, 3.0±1.0 mmol/L to 9.0±3.1, 5.0±12.4, 6.8±1.5 mmol/L respectively without significant change in high density lipoprotein cholesterol. Platelet count and volume remained unchanged after cessation of therapy and the slope and magnitude of the platelet aggregation curve in response to collagen 1.0 mg/L was unchanged whereas the amplitude of the response to collagen 2.5 mg/L increased from 17.1±4.6 Ω to 19.0±3.1 Ω without change in slope. Conclusion We concluded that atorvastatin treatment produced large reductions in TC, LDLC and TG, and that the only change seen in whole blood platelet aggregation was a small but significant reduction in the amplitude of the response to collagen 2.5 mg/L.