The purpose of this study was to investigate the changes of oxygenation in working skeletal muscle during intermittent exercise. Six healthy subjects repeated 30 bouts of intermittent cycle exercise with a work: recovery ratio of 15s: 10s. The exercise workloads were 90% and 100% of maximal oxygen uptake (VO2max). Changes in oxygenation in the vastus later-alis muscle were monitored using near-infrared spectroscopy (NIRS). Muscle oxygenation levels showed the pattern of that the decrease during every work period and the increase during recovery. From the onset of exercise at each workload, muscle oxygenation levels declined and then reached the minimum during the 2nd work period. However there was no difference between the two intensities. After the 25th pedalling a dynamic steady state for muscle oxygenation level was observed. The mean values of muscle oxygenation during last six work periods were 61.8±7.3% (mean±SD) and 54.8±11.2% at 90% and 100%, respectively. While the values for recovery periods were 79.9±8.6% and 72.7±15.0%, respectively. The values for both periods at 100%VO2max were lower (p0.05). These data indicate a consequence of the interaction between work and recovery period, and it can be considered that the NIRS curve presented here is a typical change in muscle oxygenation during intermittent exercise.