The effects of surface active agents on lipase production by Pseudomonas nov. sp. No.156 were investigated. When using a 500ml-shaking flask, lipase activity per ml. of culture broth increased with a decrease in liquid volume. Lipase activity was noted to decrease in the flask volume order of 100ml, 50ml, 25ml. While shaking the flasks, additional Adecanol LG-126 to the medium caused the differences in the extent of decrease in lipase activity according to flask volume to become less. The activity approximated that of the flasks with less liquid volume. These effects arise from an increase in the oxygen transfer rate (kLa) in the shaken flask and results in a greater production of lipase in the 500ml fermenter. Tween 60 failed to have any effect on the production of lipase and Nonion NS-215 and TM-211 were impossible to use because of accompanying blowing, even though there was high lipase activity.