Few reports have so far investigated the relationship between fibrinogen levels and the extent of coronary artery disease (CAD) as evaluated by coronary angiography, that is therefore the aim of the current study. We measured fibrinogen in 2,121 consecutive patients undergoing coronary angiography. Patients were divided in 5 groups based on quintiles of fibrinogen levels. Significant CAD was defined as stenosis >50% in at least 1 coronary vessel. We additionally measured carotid intima-media thickness (CIMT) in a subgroup of 359 patients. Patients with elevated fibrinogen were older (P = 0.038), with larger prevalence of diabetes (P = 0.027), female gender (P < 0.0001), hypertension (P < 0.001), chronic renal failure (P < 0.0001), previous CVA (P = 0.036), less often with family history of CAD (P = 0.019) and previous PCI (P < 0.0001), more often presenting with ACS (P < 0.0001), more often on nitrates (P < 0.0001), clopidogrel (P = 0.009) and diuretics (P < 0.0001). Fibrinogen levels were linearly associated with baseline glycaemia (P < 0.017), WBC count (P < 0.0001), creatinine (P < 0.0001), and Platelet count (P < 0.0001) but inversely associated with RBC count (P < 0.0001). Fibrinogen levels were associated with CAD (P = 0.001), especially for extremely high levels (5th percentile, P < 0.0001). At multivariate analysis, after correction for baseline confounding factors, high fibrinogen level (5th percentile) was still associated with the prevalence of CAD (P = 0.034). Furthermore, fibrinogen levels were related with maximal CIMT (r = 0.12; P = 0.01), with larger prevalence of carotid plaques in patients with higher fibrinogen levels (5th quintile) as compared to remaining patients (P = 0.046). This study showed that high fibrinogen level is significantly associated with CAD and carotid atherosclerosis.