Among patients consecutively admitted to a coronary care unit (CCU) without a subsequent diagnosis of acute myocardial infarction (AMI), a subgroup fo unstable angina was selected, defined as continued episodes of angina at rest during a 48-hour period, despite medical treatment in the CCU. During a four-year period, 15 patients fulfilled these criteria. Eight patients were medically treated, seven of whom developed an AMI with three subsequent deaths. Six of the infarcts occurred within eight days of admission. In six patients, fulfilling the criteria, surgical treatment was performed. Angiography and surgery in this group were associated with low incidences of myocardial infarction, late infarction and death. In one patient, surgery was declined due to unfavourable anatomical conditions. This patient subsequently developed an AMI and died. It is concluded that the combination of recent onset of angina and continued episodes of angina at rest, despite medical treatment, selects a high risk subgroup of unstable angina. Acute coronary angiography and surgery ought to be considered in this subgroup.