Five times of Kakari-Geiko practice (shadow practice) of Kendo were conducted for 30 seconds on 4 subjects. The rest between each practice was taken for 130 seconds on 2 subjects and for 100 seconds on the other 2 subjects. The heart rate and the oxygen intake were measured for 4 subjects throughout each series of practice. The maximum heart rate and maximum oxygen intake were measured by the Treadmill running for these 4 subjects. The relations between these maximum values and results measured during Kakari-Geiko were examined. The results were as follows; 1) The maximum value of the heart rate increased up to approximately 185 in Kendo practice. This value was the same as the maximum heart rate observed in a treadmill test. The heart rate at rest was recovered to 150-160. 2) The oxygen intake was nearly 2 liters in the practice. This value was 58.6-69.1 per cent of the maximum oxygen intake for each subject. 3) The oxygen debt was nearly 70-75 per cent of the oxygen intake. This showed that the Kendo practice of this kind might include a high percentage of anaerobic metabolism.