Changes in levels of plasma xanthophyll, plasma retinol, liver retinol, and liver retinylpalmitate in poults infected with Eimeria meleagrimitis or E. adenoeides were measured by high-performance liquid chromatography. Infection with either species significantly reduced total plasma carotenoids; the reduction was due largely to a decrease in xanthophyll to approximately 50% of control levels on the day of maximum effect. In addition, E. meleagrimitis infection decreased plasma retinol levels from 1.84 microgram/ml plasma (controls) to 1.00 microgram/ml plasma on day 6 postinoculation. Concomitantly, liver retinol levels fell from 0.23 microgram/mg protein (controls) to 0.15 microgram/mg protein, and liver retinylpalmitate levels fell from 0.74 microgram/mg protein (controls) to 0.44 microgram/mg protein. In contrast, Eimeria adenoeides infection caused little change in either plasma or liver retinol levels.