Event-related coherence was analyzed for 4 subjects performing a visual GO/NO-GO task. The subjects were required to push (GO) or not to push (NO-GO) a button. Twenty-one channel scalp EEGs (International 1020 system) were recorded (0.5-60 Hz) with a linked-ear reference and the surface Laplacian was estimated using the source derivation for the EEGs. Time courses of the coherence between F3 and F4, C3 and C4, P3 and P4 were calculated from 0 to 500 ms for each task. A 256 ms-window was applied to the fast Fourier transform and the window was shifted in steps of 50 ms to obtain a time course of coherence. The coherence between F3 and F4 was calculated greater in NO-GO than GO tasks. The coherence of 7.8 Hz was measured at 250 ms, and 3.9 Hz was measured at 350 ms. A high correlation between the right and left frontal lobes, as measured under the NO-GO task of inhibiting motor behavior, was suggested.