The aim of this study was to examine the relationships between cognitive functioning and blood levels of antioxidants and lipoperoxidation products in an elderly population. In 1991-1992, 1389 volunteers (574 men and 815 women aged 59 to 71 years) were recruited from the general population. Levels of selenium, carotenoids, and thiobarbituric-reactive substances in plasma and of vitamin E, glutathione peroxidase, and Cu-Zn superoxide dismutase in red blood cells were measured. Cognitive functioning was assessed with various psychometric tests. We used logistic regression to estimate the risk of poor cognitive functioning (< 25th percentile of the score distribution) associated with low values of each antioxidants (< 25th percentile) including potential confounding factors. A low level of total carotenoids (< 1.86 mumol/l) was associated with poor cognitive performance in two tests assessing visual attention and logical reasoning: the Trail-Making Test part B [OR = 1.34 IC95% (0.99-1.81), p = .055] and the Digit Symbol Substitution from the WAIS-R [OR = 1.38 IC95% (1.02-1.89), p = .04]. Low levels of other antioxidants and high levels of thiobarbituric-reactive substances were not related to poor cognitive functioning. Results observed with plasma carotenoids are in accordance with previous data obtained mostly from dietary records.