Young chickens were fed from hatching until 3 weeks of age with a white corn-soy diet (containing 1.36 micrograms total carotenoids per gram of diet) amended with a commercial preparation of lutein, a dihydroxycarotenoid, to supply 25 micrograms free lutein per gram diet. The diet which also contained 0, 1, 2, 4, or 8 micrograms aflatoxin per gram of diet was fed to four groups of ten chickens per aflatoxin treatment until they were 3 weeks old. Aflatoxin had no effect on the partial acylation of free lutein to lutein monoester that occurs in the jejunal contents of normal birds but it decreased significantly (P less than .05) the conversion of free lutein to lutein diester. Aflatoxin reduced up to 35% the lutein (94% free alcohol) content of the jejunal mucosa and the serum lutein (99% free alcohol) was reduced by up to 70%. Aflatoxin caused a slight (25%) decrease in the free lutein content of liver while increasing the monoester content 3.5-fold and the diester content 10-fold. This sequestering of lutein in the liver in esterified forms poorly transported to the integument presumably contributes to the poor pigmentation during aflatoxicosis. The forms of lutein in the toe web were diester (66%0, free alcohol (26%), and monoester (8%) and their sensitivity to aflatoxin followed the same order. These data offer clear, unequivocal proof that aflatoxin can cause poor pigmentation in birds, presumably by interfering with the absorption, transport, and deposition of carotenoids.