In order to study the possible role of β-endorphin in the pathogenesis of vitiligo, the authors measured the levels of β-endorphin in the plasma from 40 patients and the tissue fluids of skin lesions and uninvolved skin from 33 patients with vitiligo, using a 1 2 5 I RIA kit. The results showed that the levels of plasma β-endorphin in the patients with vitiligo of all of the generalized, focal and segmental types and in either progressive and stable stages were significantly higher then the normal controls. The levels of β-endorphin in the tissue fluids from skin lesions were significantly higher than those from uninvolved skin in both the local type and segmental type. In the generalized type, the levels of β-endorphin were obviously increased in both the tissue fluids from skin lesions and those from uninvolved skin. It seems that β-endorphin plays a role in the pathogenesis of vitiligo.