Recent findings suggest that erythrocyte intracellular glutathione peroxidase-1 (GPX-1) activity is related inversely to future cardiovascular events. The aim of this study is to evaluate the association of GPX-1 activity to extent of atherosclerosis, as well as its long-term prognosis in context with atherosclerotic burden. In a prospective study, we included 508 patients before coronary angiography. Atherosclerosis of carotid and leg arteries was documented using sonographic methods. Blood samples were drawn after an overnight fasting period, and GPX-1 activity was determined in washed erythrocytes. GPX-1 activity tended to decrease with increasing numbers of atherosclerotic vascular beds, so that patients without clinically relevant atherosclerosis had GPX-1 activity of 49.3 U/g hemoglobin compared with 46.0 U/g hemoglobin in patients with prevalent atherosclerosis in all 3 vascular beds (p = NS). Follow-up data (median 6.5 years) were available for 504 patients (99.2%), and 96 patients (19.0%) experienced cardiovascular events (cardiovascular death, infarction, and stroke). The event rate was inversely associated with level of GPX-1 activity divided into tertiles (hazard ratio 2.3, 95% confidence interval 1.4 to 4.0 for lowest vs highest tertile of GPX-1 activity, p = 0.002, adjusted). The highest event rate was found in persons with low GPX-1 activity and multivascular atherosclerosis (event rate 36.9%, p <0.0001). In conclusion, decreased red blood cell GPX-1 activity is associated with increased cardiovascular risk according to the extent of atherosclerosis.