The influence of unilateral n. ischiadicus lesion of conductivity on the electromyographic characteristics of the rat gastrocnemius muscles was investigated. The lesion was made by n. ischiadicus crashing. Motor and reflex gastrocnemius muscles' responses caused by n. ischiadicus stimulation (single impulses of various intensity and 0.3 ms duration) were estimated on broken and symmetric hind-limb before and 1, 5, 10, 20 and 30 days after the nerve crashing. Considerable changes of threshold and amplitude of the registered gastrocnemius muscle responses were observed ipsi- and contralaterally. It is suggested that the central dependence of processes arising in the motor centres of symmetric gastrocnemius muscles, follows unilateral n. ischiadicus lesion.