The purpose of these investigations was to measure the bulk and its sorrounding temperatures of helical involute gears operating under grease and oil bath lubrication conditions. The gear testing machine used for the tests was a closed power circuit type. All tests were made with pairs of 28 and 32-tooth gears of 2.5-module, 20-deg normal pressure angle, 25-deg helix angle of carbon steel material and HRC55∼56 hardness. The value of the loading force was changed from Pn = 0.0 to 336 kN/m in steps and the value of pitch line velocity was also changed from Vp = 1.59 to 6.19 m/s. The effects of quantities of the lubricant were also investigated experimentally. Results obtained for various greases were compared with the various oil bath lubrications.