R & D Laboratories, DAIKIN INDUSTRIES,LTD. Sakai,Osaka,Japan This paper refers to an improvement of the lubrication in a rolling piston type rotary compressor. The lubrication conditions of lubricated surfaces are examined in running compressor and some parameters of them are numerically analyzed. It is elucidated from the investigation that,when unfavorable condition occurs,the metallic contact between the journal and the bearing becomes severe, and sliding velocity at the vane-tip also gets so high,causing extremely high surface temperature of the vane-tip. It is concluded that it is very important to select proper materials for the bearings ,vane and rolling-piston. Then the materials of the 'above-mentioned parts are evaluated with two types of friction and wear testers,and selected. The selected materials are applied to an actual compressor. As the result, the compressor is successfully improved in durability.