Background: Studies have associated elevated plasma levels of the thiols homocysteine and cysteine with an increased risk of atherosclerosis. Their relationship with systemic inflammatory parameters and sclerosis scores was investigated in this study.Methods: Total homocysteine, total cysteine, neopterin and C-reactive protein (CRP) concentrations were measured in blood samples of 242 patients undergoing elective coronary angiography. A total of 181 patients had coronary artery disease (CAD), as defined by occlusion of >75% of at least one of the three main coronary arteries, and 61 subjects did not have relevant coronary stenoses.Results: Total cysteine concentrations were higher in patients suffering from coronary artery sclerosis with stepwise increases relative to the extent of coronary artery sclerosis (pConclusions: Total cysteine concentrations were well suited to estimate the extent of coronary artery sclerosis, while in our study of stable CAD patients total homocysteine was not increased compared to controls. The association between homocysteine, cysteine and parameters of immune activation and inflammation in our study suggests that these markers of CAD may be interdependent.Clin Chem Lab Med 2008;46:648–54.