Plasma concentrations of beta-carotene were determined in healthy men ingesting 180 mg beta-carotene/d during studies on the effects of beta-carotene on sunburn prevention. This dose is also used in the treatment of light-sensitive skin diseases. beta-carotene concentrations were found to reach a plateau in 1.5 to 4 wk, although there was much individual variation in the actual serum concentrations achieved. Carotenodermia was present in most subjects. No evidence of toxicity was found, confirming the findings of previous photosensitivity-prevention studies, which also reported no significant toxicity attributable to beta-carotene.