AIM: To determine the diagnostic accuracy of physicians for identifying patients with acute myocardial infarction (AMI) without an electrocardiogram (ECG). PATIENTS: All patients in Göteborg with suspected AMI below 75 years of age who called for an ambulance or came directly to one of the two city hospitals with a delay time of less than 2 h 45 min from the start of symptoms. METHODS: As part of the TEAHAT study (comparing rt-PA and placebo in AMI), we asked physicians to judge on a 1-5 scale (1 = no suspicion; 5 = convinced) how strong their suspicion of AMI was prior to interpreting the ECG. RESULTS: Among patients evaluated outside hospital with 4 or 5 on the scale, i.e. either a strong suspicion of AMI or the physician felt convinced about the diagnosis, 45% had ST elevation and 48% developed AMI during the first 3 days in hospital. The corresponding values for patients evaluated in hospital were 67 and 70%, respectively. CONCLUSION: We found that physicians could not accurately distinguish patients with AMI from those without based on clinical criteria without the help of an ECG.