We have analysed the influence of complex drug cocarnit (20 mg nicotinamide, 50 mg cocarboxylase, 0.5 mg cyanocobalamin, 10 mg disodium adenosine triphosphate trihydrate) on the nerve conduction velocity in nervus tibialis of rats with diabetic polyneuropathy. Our data shows that diabetic polyneuropathy leads to dysfunction of signal conduction to the effector. Administration of complex drug cocarnit showed linear dose-dependent therapeutic effect on pathology. After 9 d course administration in rats with diabetic polyneuropathy Cocarnit led to almost complete time parameters renewal of stimulation impulses but only with the presence of long relaxation periods between the contractions. Cocarnit has great prospects as a remedy for diabetic polyneuropathy therapy.