Objective: Strong evidence has suggested that there is a circadian periodicity of acute coronary event. Beta-blockers, aspirin and angiotensin-converting enzyme inhibitors decrease the rate of acute myocardial infarction (AMI) and blunt the peak incidence in the morning. However, such effect has not been evaluated for statins. Accordingly, the present study aimed to evaluate the influence of statin therapy on circadian variation of AMI.