AbstractBiopsy specimens of sural nerve from 10 patients with multiple sclerosis (MS), of whom only 1 was severely disabled, were assessed by morphometric techniques and compared to nerves from age‐matched controls. The frequency of abnormal teased fibers was increased in MS nerve, with many intenodes showing at least a 50% reduction in myelin thickness. Myelinated nerve fiber densities were not significantly different in MS and control nerves. Regression analysis of axonal area on number of myelin lamellae indicated a generalized reduction of myelin lamellae in this disorder. It is suggested that peripheral myelin may be involved in multiple sclerosis.Supported by the New Zealand Neurological Foundation, the Medical Research Council, and the National, Otago, and Canterbury Multiple Sclerosis Societies.