Components of the haemostatic system which may be involved in the pathogenesis of ischaemic heart disease (IHD) were measured in the Northwick Park Heart Study. Of 1510 white men aged 40-64 at recruitment, 49 have since died. 27 died from cardiovascular disease (IHD in all but 3), 18 from cancer, and 4 from other causes. The mean recruitment levels of factor VIIc, factor VIIIc, and fibrinogen were significantly higher in those who died of cardiovascular disease than in those who survived. The independent associations of factor VIIc and fibrinogen with cardiovascular death were at least as strong as the association of blood cholesterol with cardiovascular death. A clustering of two or three high clotting-factor values (factor VIIc, factor VIIIc, and fibrinogen) was present at recruitment in 63% of those who died of cardiovascular disease, compared with 23% of those who survived. The clotting-factor results appeared to be specific for cardiovascular disease: there was no evidence that high levels of factor VIIc, factor VIIIc, and fibrinogen were associated with death from cancer. The general epidemiology of factor VIIc, factor VIIIc, and fibrinogen is consistent with their having a role in the pathogenesis of IHD.