The purpose of this investigation was to determine the accuracy of the critical velocity (CV) test for predicting time to exhaustion (time limit = TL) during treadmill running. Ten adult males (mean +/- SD of age = 23 +/- 2 years) volunteered to perform a maximal treadmill test, a CV test, and five exhaustive treadmill runs at 70%, 85%, 100%, 115% and 130% of CV for the determination of actual TL. Related t-tests revealed significant (p less than 0.05) differences between the predicted and actual TL values for velocities equal to 100 and 130% of CV. The correlations between predicted and actual TL values for velocities above CV ranged from r = 0.957 to 0.980 (SEE = 0.28-0.82 minutes). At 100% of CV, the subjects maintained the running pace for an average of 16.43 +/- 6.08 minutes (range = 9.96-31.90 minutes) while, at 85% of CV, 8 of the 10 subjects were able to maintain the running pace for 60 minutes. These findings did not support the validity of the CV test for predicting the actual TL during treadmill running and indicated that, in 20% of the cases, CV overestimated the running velocity that could be maintained for 60 minutes by greater than 15%.