The role of haemostatic factors for arterial thrombosis, especially the prevalence of activated protein C (APC) resistance in patients with coronary artery disease (CAD), is controversial. Between November 1996 and August 1997, 665 patients were analyzed. Diagnosis of CAD was confirmed by coronary angiography, exclusion of CAD was accepted in the presence of negative stress testing or a negative coronary angiography. CAD was present in 370 (56%) and excluded in 295 (44%) patients. Patients with CAD were older (64 +/- 9.2 versus 57.7 +/- 16 years; P <or= 0.001), more often male [74.1 versus 48.5%; odds ratio (OR) = 3.0, 95% confidence interval (CI) = 2.2-4.2] and had a higher body mass index (27.2 +/- 3.6 versus 26 +/- 4.3; P <or= 0.001). Most conventional risk factors showed a higher prevalence in patients with CAD. An APC ratio < 2.0 showed a tendency towards a higher prevalence in patients with CAD (10.5 versus 6.4%; OR = 1.7, 95% CI = 1.0-3.0). This difference was significant in men (11.7 versus 4.2%; OR = 3.0, 95% CI = 1.3-7.1), but not in women (7.3 versus 8.6%; OR = 0.8, 95% CI = 0.3-2.2). Multiple logistic regression analysis showed an independent association of the presence of CAD with age, male gender, current smoking, arterial hypertension, lipoprotein(a) levels and an APC ratio < 2.0 (OR = 2.87, 95% CI = 1.08-8.12). APC resistance with an APC ratio < 2.0 was the only haemostatic factor that was independently associated with the presence of CAD. This association was significant only for men. It may indicate a contribution of the APC resistance to the development of CAD, which has to be proven by the follow-up.