The purposes of this study were to: (1) establish the concurrent validity of a 20-m shuttle test (20-MST) (number laps); (2) establish the test-retest reliability of 20-MST; and (3) estimate the validity of the predication equation for □O2max developed by Lerger, Mercier, Gadoury, and Lambert (1988) on female children of 10-11 years old. Seventy-six subjects underwent the 20-MST. Then 38 subjects were randomly chosen from the original 76 subjects to undergo □O2max measurement and the other 38 subjects underwent the retest of 20-MST. The results of □O2max and 20-MST were 42.66±2.67 (ml/kg/min) and 23.83±6.22 laps, respectively. The correlation coefficient of the □O2max and 20-MST was 0.75 and the 20-MST retest reliability coefficient was 0.91. The estimated □O2max which had been estimated by the predicated equation of Lerger, et al. was significantly different from the measured □O2max. In conclusion, the 20-MST is a valid predictor of cardio-respiratory endurance on female children of 10-11 years old. However, the Lerger, et al's predication equation cannot be used to estimate □O2max on female children of 10-11 years old.