The physiological responses and the magnitude of perceived fatigue (MPF) were estimated from eight healthy men during isometric continuous and intermittent handgrip at 10% maximum voluntary contraction (MVO. The physiological responses involved electromyogram (EMG), heart rate (HR), mean blood pressure (MBP) and forearm blood flow during contraction (FBFO and relaxation (FBFR). The sequence of tests included three different work patterns : 1) continuous handgrip for 30 min, 2) intermittent handgrip (10 sec contraction +5 sec relaxation) for 45 min, 3) intermittent handgrip (10 sec contraction +10 sec relaxation) for 60 min. These experiments were performed on two different heat loads (25°C and 40°C, H.R. 50%). The results were as follows : 1) The localized muscle fatigue in the forearm was observed during the work periods. 2) The mean frequency of EMG was higher at 40°C than 25°C. 3) FBFR was significantly lower than FBFC at 40°C. 4) MPF and MBP were little influenced by the heat load. 5) MPF correlated well with both HR and MBP.