Background. Increased levels of homocysteine (Hcy) and cysteine (Cys) are associated with risk of cardiovascular diseases (CVD). These thiol compounds can generate various free radicals and so cause endothelial dysfunction. Antioxidant vitamins are effective scavengers of reactive oxygen species (ROS) and prevent endothelial dysfunction. In this study, we investigated the plasma homocysteine, cysteine, vitamins E, C and A, and beta-carotene (BC) levels in cardiovascular patients to compare with controls. We also investigated whether there is a correlation between the plasma thiol compounds and antioxidant vitamins. Methods: Blood samples were collected from 47 patients with cardiovascular disease (16 women and 31 men) and 21 healthy subjects (8 women and 13 men) in the overnight fasting state. Serum thiol compound and antioxidant vitamin levels were measured by high-pressure liquid chromatography (HPLC) methods. Results: The plasma homocysteine and cysteine levels were significantly higher in patients than those of controls. While vitamin C (VC), vitamin A (VA) and beta-carotene levels were significantly lower in patients than in controls, vitamin E (VE) levels did not change in both groups. There is a positive correlation between homocysteine and cysteine levels (r = 0.622, p = 0.000) in all study population. We found that the plasma level of homocysteine was significantly correlated in negative manner with vitamins E and A levels (r = - 0.260, p = 0.033 and r= - 0.255, p = 0.036, respectively) of all study population. Plasma cysteine levels were negatively correlated with only vitamin C levels (r = - 0.320, p = 0.008) in all study populations. Conclusions: Our data suggest that Hcy and Cys are associated with cardiovascular disease and there is negative but weak correlation's between thiol compounds and antioxidant vitamins. (C) 2003 Elsevier B.V. All rights reserved.