In a prospective study of 278 consecutive patients admitted to an emergency ward for chest pain, the 115 clinical and paraclinical parameters available at the time of admission were evaluated by computer comparison with the final diagnoses. The most valuable items for making the diagnosis were classified according to their sensitivity, specificity and predictive value. Among the 278 patients, 100 individuals had myocardial infarctions (MI), 47 had unstable angina, 25 had stable angina and 106 patients had a non-coronary disease. The twelve most sensitive items for distinguishing MI from other conditions were the following: sudden onset of pain (70%); duration of more than 60 min (88%); constriction and squeezing (79%); oppression (75%); prior anginal attacks (61%); sex male (72%); age over 60 years (74%); abnormal heart auscultation (62%); abnormal electrocardiogram (ECG) (98%); segment (ST) disturbances (86%); increased glucose level (77%); CKMB fraction greater than 6% of total creatine kinase (CK) level (63%). Among the twelve most specific items, also with the best positive predictive value, irradiation in the right arm is of most importance; among the 51 patients with right arm involvement, 48 suffered from a coronary disease and 41 from a myocardial infarction. The largest extension of pain was reported in the latter group. It is concluded that chest pain with a wide irradiation involving the right arm strongly suggests that a myocardial infarction is ongoing.