As the peripheral nerve often represents the first nervous structure compromised by exogenous toxic substances at clinical and subclinical level, a neurophysiological study was carried out on 20 addicts suffering from chronic opiate intoxication. Although none of the subjects presented signs of clinically active polyneuropathy at neurological examination, an electromyographic evaluation was carried out of motor and sensitive conduction rate in the upper and lower extremities with a study of H reflex so as to ascertain possible peripheral compromise in a subclinical phase. The same study was also carried out in a control group consisting of 20 subjects, homogeneous for sex and age. Analysis of the results obtained points to a slight but statistically significant reduction in two conduction parameters which would seem to point to slight trouble in the peripheral nerve.