Tests for the investigation of peripheral circulatory function are thought, in Japan, to be of primary importance for the proper diagnosis of the hand-arm vibration syndrome. The complaints presented in connection with Raynaud's phenomenon (finger skin blanching, numbness, cold sensation, and pain in the hands) should be thoroughly assessed. In evaluating the results of skin temperature measurements and the nail compression test before and after cold provocation by immersion of the hands in cold water, seasonal and diurnal variation, as well as differences in room temperature, temperature of the cooling water, duration of cooling time, etc, must be taken into account.