1. Analysis of forms of cross-correlograms of activity of adjacent cerebral cortical neurons shows that about 85% of extreme on these graphs are symmetrically arranged relative to the origin of coordinates and that their mean width is about 30 msec. It is suggested that the main factor determining the relatively high and stable level of coordination between discharges of neighboring cortical cells is the effect of a common source, causing parallel changes in the membrane potential levels of these cells. 2. The ratio between the numbers of symmetrical and asymmetrical extreme on cross-eorrelograms of activity of remote neurons in the visual and sensomotor cortex is about 1:1. Repetitive photic stimulation changes the character of temporal relations between the discharges of these cells and the changes last at least i0 min after termination of stimulation. Aftereffects of afferent stimulation~ discovered on analysis of mutual relations between neurons in different cortical areas, indicate that synaptic connections may be present between them (including a number of intermediate cells); the effectiveness of these connections may be determined, moreover, by influences of nonspecific deep brain structures on the neocortex.