In order to assess the value of surgical revascularization of coronary arteries in patients with unstable angina pectoris, a series of 551/3397 consecutive patients belonging to New York Heart Association (NYHA) class IV was investigated. Fulfillment of at least two of the following criteria is mandatory for diagnosis unstable angina pectoris: slightly increased CK (< 300 IU/l), modified ECG at rest (decreased ST-T, increased ST), therapy-resistant post-infarction angina, therapy-resistant angina at rest, increased severity, duration or frequency of angina attacks within the last three months, insufficient therapeutic response. Patients with acute myocardial infarction were excluded from analysis. 362/551 patients out of the investigated cohort fulfilled criteria of unstable angina pectoris NYHA class IV; in 189/551 patients, criteria of stable angina pectoris NYHA class IV were fulfilled (controls). The mean follow-up period for these patients was 72 +/- 33 months (24 +/- 144 months). There were no differences regarding age, percentage of patients with three vessel disease, ejection fraction of the left ventricle and of cardiogenic shock. The mean number of aortocoronary grafts was 3.8 +/- 1.3 in patients with unstable angina, compared to 3.4 +/- 1.5 in patients with stable angina pectoris (p < 0.05). An intra-aortic balloon pump had to be applied in 8% of patients with unstable angina compared to 3% in stable angina. A mortality of 2% within 30 days of surgery was registered in unstable compared to 3% in stable angina pectoris (n.s).(ABSTRACT TRUNCATED AT 250 WORDS)