Background Oxidative stress, which is thought to be increased in subjects with various coronary risk factors, induces thioredoxin (TRX), a redox-active protein. Methods and Results To determine whether oxidative stress is increased, serum concentrations of both TRX and α-tocopherol (vitamin E) were determined in 12 control subjects without any coronary risk factors (CONTROL), 6 current smokers (SMOKING), 19 hypertensive patients (HT), 7 hypercholesterolemic patients (HC) and 14 subjects with multiple risk factors (MULTIPLE). Patients with diabetes mellitus were not included. The serum TRX concentrations (mean ± SD ng/ml) were significantly higher in SMOKING (41±10), HT (41±17), HC (48±15) and MULTIPLE (46±15) than in CONTROL (24±11). The serum α-tocopherol concentrations (mg/g lipids) were not significantly different among CONTROL (4.0±0.7), SMOKING (4.0±0.8), HT (4.1±0.6) and HC (4.2±0.6), although the concentration was significantly lower in MULTIPLE (3.3±0.7) than in any of the other study groups. Conclusions SMOKING, HT, HC and MULTIPLE had significantly higher serum TRX concentrations than CONTROL, suggesting increased oxidative stress. MULTIPLE had a lower serum concentration of antioxidant α-tocopherol than any of the other study groups, suggesting impaired or exhausted defense against chronic oxidative stress in the presence of the multiple risk factors. (Circ J 2005; 69: 291 - 294)