The horseshoe-bat Rhinolophus ferrumequinum is the best known representative of those bats using constant frequency sounds for echolocation. Schnitzler (1968) has shown, that horseshoe-bats compensate Dopplershifts during flight by lowering the emitted constant frequency so that the heard echofrequency always remains at about 83.4 kHz. His results suggest that horseshoe-bats use the constant frequency part of their orientation sounds for detection and measuring of flight velocities by means of Doppler shifts. The investigation reported here intends to give some clues how constant frequency echoes are processed in the main auditory centre, the colliculus inferior, and how Rhinolophus extracts information for orientation from these echo signals.