The study examined whether the aerobic fitness level modifies the cerebral oxygenation response to incremental ramp exercise, and more specifically the decline in cerebral oxygenation from heavy exercise up to maximal intensities. 11 untrained (V˙O2max 47.3±4.0mLmin-1kg-1) and 13 endurance-trained (V˙O2max 61.2±8.0mLmin-1kg-1) healthy men performed a maximal ramp cycle exercise. Left prefrontal cortex oxygenation ($δ$HbO2) was monitored by near-infrared spectroscopy. A cerebral oxygenation threshold decline (ThCOx) during exercise was determined. ThCox occurred in all subjects but for higher V˙O2 (mLmin-1kg-1) in endurance-trained than in untrained subjects (P<0.01). At submaximal exercise intensity corresponding to ThCOx, $δ$HbO2 was higher in endurance-trained than in untrained subjects (P<0.05). V˙O2 at ThCox was related to V˙O2 at respiratory compensation point (n=24, r=0.93, P<0.001) and to V˙O2max (n=24, r=0.92, P<0.001). These findings indicate that above the respiratory compensation point the prefrontal O2 demand exceeds the supply in untrained and in endurance-trained subjects. In addition, the occurrence of ThCOx was delayed to higher absolute exercise intensities in endurance-trained in relation with their higher V˙O2max than untrained men. These results demonstrated that aerobic fitness influences cerebral oxygenation during exercise.