Summated visually evoked potentials (VEPs) from the dorsal lateral geniculate nucleus (GL), striate cortex area 17 (VC-17), circumstriate visual cortex area 19 (VC-19) and the inferior pulvinar (PuI), together with single unit responses from the inferior pulvinar, were recorded in seven squirrel monkeys during repeated sessions in the dark-adapted state, under stimulus conditions which varied the luminance of diffuse unpatterned flashes and varied the contrast border and contour density of patterned flashes which were equated for luminance. These recordings, except for the unit responses of the inferior pulvinar, were contrasted with VEPs from the same sites and under the same stimulus conditions in the light-adapted state. In addition, VEPs, and also unit responses from the inferior pulvinar, were recorded in the absence of eye movements during a terminal paralyzed state under gallamine triethiodide and tubocurarine and compared with the VEPs obtained under the same stimulus conditions during the non-paralyzed state. In the non-paralyzed state with head fixed but eyes free to move the following results were obtained. As expected, the higher of two luminance levels used with diffuse flashes produced generally larger amplitude VEPs from all recording sites. Therefore, a standard luminance level was selected for unpatterned diffuse flashes and the average luminance of each of the patterned stimuli (two sizes of black and white checkerboard squares and two widths of black and white vertical striations, with the two sizes of squares and stripes measuring 4.3° and 1.1° of visual angle) was equated to that of the standard diffuse flash. No differences in the VEPs from the dorsal lateral geniculate nucleus were observed between unpatterned diffuse flashes and any of the patterned flashes in either the dark-adapted or light-adapted states. For each of the other recording sites (VC-17; VC-19; PuI) under both dark-adapted and light-adapted states there were marked differences in the waveform and amplitude of VEPs for unpatterned and patterned stimuli, especially those patterned flashes of higher contrast border and counter density (small checkerboard squares and fine vertical striations — CB 1.1° and VS 1.1°). These differences were not observed in the paralyzed state with general muscular paralysis and all eye movements eliminated. Post-stimulus time histograms for single units recorded in the inferior pulvinar under both non-paralyzed and paralyzed states showed differences between unpatterned diffuse flashes and patterned flashes. Patterned flashes showed a higher concentration of unit discharges around modal points in time. The highest rates of firing were associated with patterns having higher values of contrast border. Unit responses recorded in the inferior pulvinar tended to have three distinct latencies of modal rate of discharge which corresponded generally to the peak latencies of three of the components of the VEPs recorded in the inferior pulvinar.