The performance-enhancing effects of Pseudosasa japonica were investigated in mice using an adjustable-current water pool. Compared to the control group, a 1.5-fold increase in swimming time was observed in the mouse group administered an 80% ethanol extract (PJE) of the leaves of P. japonica. The blood lactate level, an important indicator of fatigue, was significantly lower (28%, P<0.05) in PJE group than in the control group. These results suggest that PJE possesses stimulatory effects that can enhance exercise endurance and reduce fatigue.