By applying a combined method of crosscorrelation and frequency analysis to EEG tracings, the average response patterns to photic flicker stimulation with a frequency in the alpha wave range were sorted out, even when the application of the frequency analysis only could not separate the response from the irrelevant oscillations to the stimulation. During the stimulation, low volage fast pattern (alpha blocking state), in which the response was hard to recognize by visual inspection of the tracing, occurred in the EEG tracings from time to time. In the frequency spectra of them, however, not only a peak at the stimulating frequency, but the other ones at slightly higher frequency and sometimes with subharmonic frequency were appeared to suggest they are the response to the stimulation, though they are far lower than the peak of the dominant alpha wave before the initiation of the stimulation, rised up at the stimulating frequency in the power spectra of the crosscorrelogram between the stimulation and the tracing to indicate the other peaks were not related response, at least directly, to the stimulation, but by others
