Background: When cells or organisms are exposed to environmental stresses, they respond by synthesizing a characteristic group of proteins called heat shock proteins(HSP) or stress proteins. In a variety of HSP, the so-called HSP 70 family is the most prominent, conserved, and best characterized. The HSP 70 family is required for survival of cells during and after thermal stress. Objective : The purpose of this study is to investigate if the cultured human melanocytes and rnelanotic malignant melanoma cell lines(SK 30) expressed HSP 70 family unstressed, after heat shock and ultraviolet exposure. Methods : Protein was isolated from melanocytes and SK 30. Western blotting was done for identification of the HSP 70 family. Resutts : HSP 70 family expression could be detected in the unstressed cultured human melanocytes and SK 30(malignant melanoma cell lines). HSP 70 family expression inereased in the melanocytes and SK 30 after heat shock. Irradiation of the melanocytes with UVA resulted in a decrease in expression of HSP 70 family after 32, 48 J/cm compared with 4, l6 J/cm. Irradiation of the melanocytes with UVA + B resulted in a dose-dependent increase in expression of HSP 70 family but a decrease in expression of HSP 70 family after 80mJ/cm. Irradiation of SK 30 with UVA resulted in a dose-dependent decrease in expression of the HSP 70 family. Conclusion : HSP 70 family expression was detected even unstressed. This high base line HSP 70 family expression may suggest that melanocytes have ability to protect from environmental stresses like keratinocytes. (Kor J Dermatol 1996;34(2) : 208~211)