Electrophysiological tests have been carried out in 57 flux division workers aged from 24 to 59 years, 37.6 on average, and employed in manganese dioxide exposure for 3 to 35 years, 13.1 on average. The control group consisted of 22 healthy subjects with no occupational exposure to toxic substances, aged from 26 to 63 years, 39.5 on average. The conduction rate in motorial and sensory fibers of 3 peripheral nerves was tested and electromyogram from 2 distal muscles was made. The EMG apparatus produced by the DISA 1500 firm was applied in the studies. The rate of conduction in motorial fibres was found to be reduced in 23 workers, which constitutes 40%, whereas in sensory fibres--in 32 subjects (56.1%). The electromyogram exhibited concurrent denervation with changed motorial conduction in the nerves innervating the mentioned muscles in 21 subjects (36.8%).