To evaluate whether ET secreted from keratinocytes under the UV irradiation works as paracrine effects such as melanocyte proliferation and function, the present study was undertaken. Cultured human keratinocytes were irradiated with UUVB 50mJ/cm 2 . Twenty fours hours later, conditioned medium of keratinocytes was added into the growth medium of melanocytes. Four days later, in order to detect of melanocyte proliferation and function, number of melanocytes, melanin granules and tyrosinase activity were measured.1. The number of melanocytes were high increase in groups of incubation with conditioned medium of irradiated keratinocytes.2. The melanin contents were significant increase in groups of incubation with conditioned medium of irradiated keratinocytes.3. The tyrosinase activity of melanocyte incubated with of conditioned medium from cultured keratinocyte irradiated with UVB was relatively increase than that of melanocyte incubated with conditioned medium from cultured keratinocytes irradiated with UVB and treated with Anti-ET-1.These findings suggest that keratinocyte derived ET-1 make a considerable effect on human melanocyte proliferation and function in UV melanogenesis.