The penetration of zinc through normal skin treated with a zinc oxide (25%) medicated occlusive dressing was studied. The mean release rate of zinc to the skin was 5 micrograms/cm2/h. After 48 h of treatment suction blisters were raised by the "Kiistala method." The zinc concentration of the epidermis, blister fluid and dermis was increased beneath the zinc dressing compared to control-treated skin. The study shows that zinc permeates intact human skin from topically applied zinc oxide in vivo.