The mercury concentrations in fumarolic gas condensates collected from volcanic areas in Hokkaido, Miyazaki, and Kagoshima Prefectures, Japan, were investigated. Mercury concentrations ranged from 0.12 to 135 ug l-1 in 44 collected samples. It was found that there was a positive correlation between mercury and chloride concentrations in fumarolic gas condensates collected from Satsuma-Iwojima Volcano, Kagoshima Prefecture. It was considered that the mercury in fumarolic gas was discharged in the form of mercury (I or II) chloride. However, the results from mercury chemical equilibrium calculations for the vapor in fumarolic gases indicated that mercury was discharged mainly in the form of metallic mercury vapor.