Estrogen and androgen receptors were investigated in 55 male and 11 female volunteer patients with acne, the samples of efflorescence bearing skin and of normal skin being biopsied and kept frozen in liquid nitrogen until assayed. For the determination of androgen and estrogen receptors the saturation analysis was used. The level of testosterone and estradiol in blood was measured in the same patients with the aid of radioimmunoassay. As a control a skin of the same age was used. Of the male acne patients 52% were estrogen-receptor positive in the acne-lesions and 51% positive in their normal skin, while only 18% of the normal male controls were positive. Of the female acne patients 25% and 66% were estrogen receptor positive in their efflorescences and normal skin, respectively. Of the female normal controls 33% were estrogen receptor positive. No correlation could be demonstrated between the steroid receptor concentration and the hormone serum levels. The determination of androgen receptors showed a positive result in 50% of the male patients in the lesions and 60% in the normal skin. Normal male controls were androgen receptor positive in 27%. Of the female acne patients 25% were androgen receptor positive in the lesions and 17% in their normal skin. Of the female controls 23% were androgen receptor positive in the skin. It was concluded that the whole skin of acne patients has a higher target organ sensitivity than the skin of normal controls of same age. The missing correlation between hormone serum levels and receptor levels suggests an independent hormone-metabolism of the skin. The meaning of the occurrence of estrogen receptors in acne lesions and normal skin has to be further investigated.