Duration of prehospital delay in patients with acute myocardial infarction (AMI) is receiving increasing attention given the time-dependent benefits associated with prompt use of coronary reperfusion strategies. To examine trends (1986-1997) in time to hospital presentation and factors associated with prolonged delay in a community-wide study of patients with AMI. Longitudinal study of 3837 residents of the Worcester, Mass, metropolitan area hospitalized with AMI in 7 one-year periods between 1986 and 1997 in whom information about prehospital delay was available. The mean, median, and distribution of delay times exhibited either inconsistent or no changes over time. In 1986, the mean and median prehospital delay times were 4.1 and 2.2 hours, respectively; these times were 4.3 and 2.0 hours, respectively, in patients hospitalized in 1997. Overall, with no significant differences noted over time, approximately 44% of patients with AMI presented to area-wide hospitals in less than 2 hours after the onset of acute coronary symptoms. Increasing age, history of angina or diabetes, onset of symptoms in the afternoon or evening, and hospitalization in the most recent study year (1997) were significantly associated with delays of more than 2 hours in seeking hospital care after controlling for a variety of factors that might affect delay. The results of this population-based study suggest that a large proportion of patients with AMI continue to exhibit prolonged delay. The characteristics of many of these individuals can be identified in advance for targeted educational efforts. Arch Intern Med. 2000;160:3217-3223.