The purpose of this study was to analyse electromyographic characteristics of Tai Chi. The subjects, six healthy men, performed ; (1) the maximum voluntary contraction (MVC) of each tested muscle ; (2) three forms in 24-style Tai Chi ; (3) on a bicycle ergometer (100 w) and jogging (120 m/s). For each muscle, the maximum integrated EMG for one second was computed and standardized by MVC(%MVC). The results were as follows : (1) High muscle activity was observed during Tai Chi. In five muscles, the %MVC exceeded 60%. (2) In the rectus femoris m., the %MVC of Tai Chi was 6.8 times that of the bicycle ergometer and 10.3 times that of jogging (p<0.01). In a similar way, in the tibialis anterior m., the %MVC was 7.1 and 4.8 times (p<0.01), and in the rectus abdominis m., the %MVC was 6.3 and 4.9 times (p<0.01). We conclude that Tai Chi might be useful as an exercise in muscle strength training.