Plasma concentrations of beta-carotene and retinol after supplementation of children with beta-carotene in supplements and in foods were compared in Guatemalan children. The children received 6 mg/d beta-carotene [1000 retinol equivalents (RE)] as purified supplements or as carrots for 20 d and the effects on plasma beta-carotene and retinol concentrations were assessed. Plasma concentrations of beta-carotene were increased by 0.59 +/- 0.65 and 0.60 +/- 0.67 mumol/L after supplementation with beta-carotene capsules for 10 and 20 d, respectively. Addition of cooked carrots to the diet resulted in no significant change in plasma beta-carotene. Fasting plasma retinol concentrations were 1.23 +/- 0.35 mumol/L and were not significantly changed in response to supplementation with either of the carotene treatments with retinyl palmitate (1000 RE/d) for 20 d. Possible explanations for the differences in effects of plasma concentrations between the two methods of supplementation are discussed.