Changes in seven plasma carotenoids were measured in 30 men for 11 d after ingesting a single dose of pure beta-carotene or a high carotenoid vegetable. A controlled, low-carotenoid diet was fed in a crossover design. Maximum plasma concentrations of beta-carotene occurred 24-48 h after dosing with beta-carotene (12 or 30 mg) or carrots (270 g). A large intake of broccoli (600 g) or tomato juice (180 g) did not change any plasma carotenoids. We concluded that 1) normal subjects vary widely, three to fourfold, in efficiency of carotenoid absorption; 2) peak plasma response to beta-carotene in a capsule occurs at 24-48 h; 3) a large single intake of carrots produces a small increase in plasma beta-carotene but single intakes of broccoli or tomato juice do not change plasma carotenoids; and 4) plasma response to pure beta-carotene is greater than the response to a similar amount of beta-carotene in carrots.