Background and Aim: Low serum levels of antioxidant vitamins are associated with coronary artery disease (CAD). An immunomodulatory effect of antioxidants has been proposed. The aim of the study was to investigate whether an increased immune response in CAD patients was associated with suppressed circulating levels of antioxidant vitamins. Methods and Results: Forty-four men with stable angina and angiographically verified CAD were included as well as 69 healthy controls. T cell subsets in peripheral blood were quantified by 3-colour flow cytometry. C-reactive protein (CRP), soluble interleukin-2 receptor (sIL-2R) and the lipophilic antioxidants a-tocopherol, ß-carotene and lycopene were determined in serum. Compared with controls, patients had signs of an enhanced inflammatory activity assessed by significantly increased levels of CRP, sIL-2R and CD4+CD25+T cell subsets. Patients also had significantly lower ß-carotene and lycopene levels whereas a-tocopherol levels did not differ. The increased inflammatory/immune parameters in patients showed a significant inverse relationship to serum ß-carotene but not to lycopene or a-tocopherol. Conclusions: Low serum ß-carotene in CAD patients reflects activation of the immune system. Inflammation should be considered as an important confounding factor when analysing data on ß-carotene and CAD. © 2003, Medikal Press.