29 patients were examined during a therapy with beta blockers. The medication was applied over 12 weeks, 16 patients received propranolol 120 mg/day, 13 patients metoprolol 200 mg/day. Two patients showed side-effects. Neurophysiological examinations, i.e. sural nerve conduction velocity and paired stimulation of the sural nerve, revealed a slight decrease of nerve conduction velocity and a significant increase of the latency prolongation of the second nerve action potential when the medication was finished. These functional changes in the sural nerve may result from the interaction of metoprolol and propranolol with beta-receptors of the peripheral nerve.