Plasma levels of the prothrombin activation fragment 1 + 2 (F 1 + 2) and of thrombin antithrombin III complexes (TAT) were determined in 225 patients with angina pectoris undergoing coronary angiography. Oral anticoagulant therapy was associated with a marked reduction in mean F1 + 2 (0.63 vs 1.62 nmol/l, p < 0.0001) and TAT levels (1.65 vs 2.23 micrograms/l, p < 0.0001). Omitting patients on oral anticoagulants, TAT values showed a positive association with patients' age (r = 0.18; p = 0.01) and were slightly higher in patients with a history of myocardial infarction than in those without (2.47 vs 2.11 micrograms/l; p = 0.06). Both F1 + 2 and TAT levels were increased in patients with angiographically verified coronary atherosclerosis as compared to patients with angina and angiographically normal coronaries (F1 + 2: 1.76 vs 1.36 nmol/l, TAT: 2.35 vs 2.00 micrograms/l; p-values after adjusting for age, sex and past history of myocardial infarction 0.06 and 0.11 respectively). However, no graded relationship between F1 + 2 or TAT values and severity of atherosclerosis was observed. This study provides suggestive evidence that a procoagulant state exists in patients with angina pectoris and coronary atherosclerosis. Its relevance in predicting coronary ischaemic events needs to be studied prospectively.