Nine healthy men with type IVa or Va male pattern baldness completed a 4-month single-blinded controlled pilot study designed to assess the effect of ultraviolet light (UVL) on topical minoxidil-induced hair growth. Subjects applied 2% topical minoxidil solution twice daily to their balding scalps and to one target area on the upper arm. These men, all of whom had either skin type II or III, were randomized to also receive either incremental doses of UVB or PUVA (topical psoralen) twice weekly to one side of their scalp and to a 2.5 cm target area on the nonminoxidil-treated upper ipsilateral arm. Vellus, nonvellus, and total hair counts were done in two 1-inch in diameter circular target areas in symmetric regions of the scalp and on each upper arm at regular intervals. All nine subjects had an increase in target nonvellus hair and a net loss of vellus hair in scalp target area treated with topical minoxidil. Concomitant UVL did not have a significant synergistic nor adverse effect on topical minoxidil-induced hair growth.