On 40 healthy male volunteers with different pigmentation level (Caucasians: skin types I-III, negroes: skin type VI) the basal alpha-MSH-secretion as well as the influence of UV-A-wholebody-irradiation (6 J/cm2) on alpha-MSH-serum concentration were measured. The mean basic values of red-haired and blondes are with 73,0 respectively 71,6 pg/ml significantly lower than the mean values of negroes with 99,6 pg/ml. After UV-A-irradiation the alpha-MSH mean values within one hour among red-haired persons increase 26,7%, among blondes increase 22,6%. Dark-haired caucasians (skin type III) as well as negroes show no significant changes in alpha-MSH serum level. These results support a peripheral sensor for UV-A-rays which induce a hypothalamic-pituitary response (alpha-MSH secretion) obviously on a nervous way. One can point out that genetic and/or racial characteristics influence this central-nervous reaction due to UV-A-irradiation of the skin. The connection between the development of malignant melanoma and the UV-A-induced changes of alpha-MSH level is discussed.