The occipital EEG was observed under the rhythmic photic stimulation (F) at 7.5, 9.2, 11.4, 15.0 and 22.5Hz as well as under the nonflicker (NF) stimulation for 11 human adults. The data were frequency-analyzed with a Waltertype apparatus and the obtained integrated values in 10-sec units for 7 frequency bands (theta 1 and 2, alpha 1, 2 and 3, beta 1 and 2) were used as cortical responses. The spontaneous or NF activity was blocked by eye opening (EO) for all bands, particularly for the alpha band in which the S's spontaneous alpha activity was included. The same blocking effect (I) was observed by flicker both with eyes closed and opened, and this effect was relatively independent of flicker frequency. Thus, the nonspecific I effect was estimated per band, and the frequency-specific effect (FE) was computed by additing the absolute value of I to the difference in the cortical response between F and NF; that is, FE=(F-NF) +I. The obtained FE spectrum in relation to the NF spectrum was little affected by EO, was only a little different, if any, between the dominant alpha and the poor alpha subjects, and had a wider distribution with a higher mode (alpha 3 rather than alpha 2).