This study investigated the clinical characteristics of acute myocardial infarction (AMI) complicated by recurrent ischemia, especially relating to the electrocardiographic ST changes during the attacks. Fifty-six patients with AMI were complicated by recurrent ischemia (ischemia group), and 238 were not (non-ischemia group). The ischemia group was preceded by prior episodes of angina or myocardial infarction in 88%, as compared with 65% in the non-ischemia group (p less than 0.05). There were non Q wave infarction in 45% of the ischemia group, and 24% of the non-ischemia group (p less than 0.05). The overall in-hospital mortality rate was similar in the ischemia group (13%) and in the non-ischemia group (17%), although the causes were predominantly pump failure in the former and cardiac rupture in the latter. ST segment elevation occurred in 29 patients and ST depression occurred in 26 patients of the ischemia group during the attacks. Multivessel coronary arterial lesions were more frequently present in the latter subgroup than the former (38% vs 79%, p less than 0.05). The in-hospital cardiac deaths were also more frequently noted in the latter subgroup. Recurrent ischemia after AMI with concomitant electrocardiographic ST depression is a high risk subgroup, and, therefore, aggressive revascularization procedures may be indicated in such cases if suitable.