Patients with cystic fibrosis (CF) have significantly decreased plasma concentrations of antioxidant vitamins which is considered to result both from fat malabsorption and from chronic pulmonary infection. The aim of this study was to investigate levels of vitamin A and beta-carotene in plasma of CF subjects with pancreatic exocrine insufficiency. In thirty CF patients mean plasma concentrations of vitamin A (1.17 micromol/l) was lower by 30% and that of beta-carotene (1.3 micromol/l) by 60% than in healthy children. Vitamin A level was positively correlated with beta-carotene (r=0.67; p<0.001). Ratios of beta-carotene to total cholesterol and cholesterol of LDL (low density lipoprotein) were 40% lower than in the control group. We conclude that in our CF patients the concentration of beta-carotene does not seem to be sufficient to inhibit lipid peroxidation especially of LDL fraction.