Interactive effects of an oral dose of equal quantities of beta-carotene and either canthaxanthin or lycopene on serum and tissue beta-carotene accumulations were investigated in domestic ferrets. Like humans, ferrets absorb a substantial portion of ingested beta-carotene intact and accumulate it in tissues. After the ferrets ingested a low carotenoid purified diet for 13 d, they were randomly assigned to one of two groups of six animals. One group was dosed with beta-carotene (10 mg/kg body weight) and the other with beta-carotene and either canthaxanthin (Experiment 1) or lycopene (Experiment 2) (10 mg/kg body weight for each). In Experiment 1, ferrets that received a combined dose of beta-carotene and canthaxanthin had serum beta-carotene concentrations that were significantly lower at 8, 12 and 24 h post-dosing (P < 0.05), compared with those that received an individual dose of beta-carotene; liver, adrenal and kidney beta-carotene concentrations were also significantly reduced. In Experiment 2, ferrets that received a combined dose of lycopene and beta-carotene had lower serum and tissue beta-carotene concentrations than in those that received beta-carotene alone; the differences were not statistically significant with the exception of serum beta-carotene concentrations at 24 h post-dosing. The results suggest that, at the doses given, a concurrent oral canthaxanthin dose has a specific antagonistic effect on the bioavailability of a beta-carotene dose in ferrets.