The effect of microelectrophoretically applied glutamate on the background activity of sensorimotor cortex neurons located 80-250 μm from the application point was studied in nembutal anesthetised cats. When glutamate was applied at a distance of up to 100 μm from the recorded neuron, most units responded with excitation, which might be the effect of glutamate as an excitatory transmitter. Within the distance ranging from 100 to 200 μm 57% of neurons revealed inhibition of the background activity. At 200-250 μm inhibition occurred in 70% of the neurons examined. Picrotoxin application within the vicinity of the recorded neuron reduced the inhibition evoked by glutamate.