ABSTRACT. The average amounts of seasonal snow cover and snowfall in Japan were calculated as 7.9 x 1013kg and l.2 x 10 14 kg, respectively. The mass of seasonal snow cover of a heavy-snowfall winter, 1980-81 (56-Gosetsu), was calculated as l.3 x 1014kg. The amount of7.9 x 10 13 kg was converted to water equivalent of230 mm on the whole snow-covered area, including snow-prone area. A mean of 370 mm in snow water equivalent was calculated for the snow area where mean snow depth on the ground was more than 10 cm.