The study of the 40 Hz activity of the brain which was begun by Adrian (1942) has been furthered for the past years with several new approaches: A neural model for the generation of 40 Hz activity in attention has been published by Freeman (1975) whereas new possibilities in clinical applications and exploration of cognitive processes in an extended manner was proposed by Galambos and coworkers (1981). The present study demonstrates the relation between 40 Hz spontaneous activity in human EEG-recordings and the middle latency response of the auditory evoked potentials. The applied signal analysis method allows also a single trial analysis of EEG-EP epochs which can be extended in studies on cognitive processes. A perspective concerning the middle latency response of the auditory AEP is also given.