The seasonal variations of skin temperature, skin pH, evaporative water loss (EWL) and skin surface lipid values were determined in the forearm skin of 24 healthy Japanese adults at four different periods over one year. The results provide new information on the changing systemic patterns of the four skin parameters. It was found that EWL, total lipid and squalene values in July were approximately 2-3 times those in January. On the other hand, the skin pH was significantly lower in July than in January, April or October. However, the extents of change of skin pH and cholesterol values were less than those of EWL, squalene and total lipid values on the basis of statistical analysis. Furthermore, significant correlations were observed between skin temperature and EWL, total lipid and squalene values. On the other hand, significant inverse correlations were found between skin pH and skin temperature and EWL values. On the basis of these results, the dependence of sebaceous lipids on skin temperature and the contribution of eccrine sweating to the skin pH are discussed.