The amount of atmospheric ozone was measured at Tokyo during the period from January 1951 to September 1952, using a chromium photo-electric tube and glass filters (R. Stair's method). According to the results of observation, the amount of atmospheric ozone shows a marked seasonal variation having the maximum value in late spring (about 0.28 cm) and the minimum value in fall (about 0.22 cm). This agrees fairly well with the results obtained by other observers in similar latitudes. Relations between the deviation 98 Journ.