The previous studies relating to athletic ability and rapid weight loss produced conflicting results, which may be explained by different testing items or subject and varied level, method, duration of rapid weight loss regimen. The purpose of this study was to investigate the effect of a 4-day regimen of dietary restriction and exercise, induced at least four percent weight loss, on athletic ability of boxers. Nine boxers were administered maximum hand-grip strength(muscular strength),sum of 6-minute hand-grip strength (muscular endruance), Margaria-Kalamen power test(power),50-yard dash(speed),boxing3-1-3-1-3 minute walk-run(cardiovascular endurance)and plasma volume under conditions of before and after body weight loss. The results obtained by Dependent t-test showed no significant decrease (P.＞05) in muscular strength, muscular endurance, power, speed, cardiovascular endurance and plasma volume before and after a 4-day regimen of dietary restriction and exercise. It was concluded that athletic ability of boxers also can maintain a high level after a 4-day regimen of dietary restriction and exercise, which induced four percent weight loss.