To determine the prevalence and characteristics of acute myocardial infarction (AMI) patients who present to emergency departments with normal or nonspecific electrocardiograms (ECGs), data were analyzed from 7,115 consecutive patients in the Multicenter Chest Pain Study. AMI patients with normal or nonspecific initial ECGs (n = 107) were less likely to have a past history of coronary artery disease or to be diaphoretic on presentation (p less than 0.01) than AMI patients with initial ECGs highly suggestive of AMI (n = 811). The overall probability of AMI among patients with chest pain and initially normal or nonspecific ECGs was 3%, but ranged from less than 1 to 17% depending on the patient's age and sex and whether the patient had pressure-type pain or pain radiating to the shoulder, neck or arms. Among initially admitted patients, the time elapsed between onset of pain and presentation was similar in both groups. However, the time between onset of pain and definitive diagnosis of AMI by enzymes or clinical course was longer in patients with initially normal or nonspecific electrocardiograms (8.3 vs 7.5 hours, p less than 0.05), their peak creatine kinase levels were lower (mean 643 vs 1,032 mg/dl, p less than 0.001) and their mortality was slightly lower (6 vs 12%, p = 0.10). These findings suggest that AMI patients with initially normal or nonspecific ECGs may have a less severe short-term clinical outcome.