Twenty-five male volunteers were tested isokinetically for knee extension fatigability. A series of 10 maximal knee extensions were performed at 4 different contractile velocities: 60 degrees, 150 degrees, and 300 degrees/sec. Isokinetic fatigue curves were plotted for each of the test conditions. The degradation of torque values was expressed as a percentage of each subject's maximum torque value at that particular contractile speed. The results of the investigation indicate that (1) the isokinetic fatigue curve for knee extension appears to be linear during the initial stages of the fatiguing process; and (2) fatigue curves for knee extension appear to be identical regardless of the contractile velocity selected for investigation.