Therapeutic defibrination by Arwin was induced in a group of nine patients suffering from unstable angina combined with hyperfibrinogenaemia and in a further six patients who developed hyperfibrinogenaemia accompanied by angina pectoris after thrombolytic therapy with streptokinase for recent myocardial infarction. In patients of the former group with unstable angina a mean pretreatment plasma fibrinogen concentration of 4.9 g/1 was lowered to 1.4 g/l over a period of four weeks, whilst in the latter group, the plasma fibrinogen was lowered from 5.7 g/l to 2.0 g/l over 10 days. In all cases a remarkable improvement in the severe anginal symptoms was achieved already at fibrinogen levels within the lower range of normal. This improvement outlasted the period of therapy in most patients. Two patients died following acute myocardial infarction; one of the patients with unstable angina died 15 months after Arwin therapy and the second patient discontinued therapy after one week and died three weeks later.