Abstract： Background Hypertension,diabetes mellitus,hypercholesterolaemia and current smoking are the strongest modifiable cardiovascular risk factors for acute myocardial infarction (AMI).We examined their changing trends over the last 20years.Methods The clinical data of 3498 patients hospitalized in Peking University People's Hospital with AMI from 1991 to 2010 were used.Information was collected regarding to patients' demographic data,cardiovascular risk factors (hypertension,diabetes mellitus,hypercholesterolemia and current smoking).To assess trends over time in the prevalence of risk factors,we categorized patients into four groups (1991 to 1995,1996 to 2000,2001 to 2005 and 2006 to 2010).Results Highly significant increases were observed in the prevalence of hypertension from 40.8％ to 55.6％ for males and from 58.0％ to 69.0％ for females; and diabetes mellitus from 12.9％ to 30.8％ for males and from 23.0％ to 42.3％ for females.Similarly,the prevalence of hypercholesterolaemia decreased from 53.1％ to 30.7％ for males and from 57.0％to 44.0％ for females.The prevalence of current smoking decreased in females from 29.0％ to 11.1％,but remained unchanged in males.In addition,the proportion of patients with more than three modifiable risk factors increased from 19.0％ to 27.1％ and the age at onset of AMI extended to younger as well as older individuals.Conclusions The prevalence of hypertension and diabetes mellitus are still increasing in patients with AMI in Beijing and although the prevalence of hypercholesterolaemia and current smoking decreased,high clustering of risk factors were commonly present.These adverse trends show a compelling need for more effective management of cardiovascular risk factors.