The value of thorough examination of the case history as a diagnostic tool on hospitalization of patients with suspected myocardial infarction was investigated in three independent prospective studies. Use of a limited number of pain-related elements (= 'criteria'), that had already been obtained in the emergency room, could improve the decision on whether or not to admit patients to the coronary-care unit. As an example, in one of the studies, use of such criteria would have reduced the number of 'unnecessary' coronary-care-unit admissions from 298 to 162, a 46% reduction (P less than 0.001). In the same patient sample, use of the criteria could have reduced the number of patients with definite acute myocardial infarction, admitted to the general wards, from 47 to 22, a 53% reduction (P less than 0.01). These favourable results were confirmed in the two independent, smaller-scale studies.