The superficial peroneal nerve from 46 elderly patients was studied by light and electron microscopy. Like most elderly people, these patients displayed evidence of varying degrees of peripheral nervous system dysfunction, but they were not suffering from any disease known to alter the peripheral nerve. A quantitative study showed that myelinated fiber loss predominated in the large diameter group. In the majority of cases, clusters of regenerating myelinated fibers were numerous. On the other hand, Wallerian-like degeneration aspects, segmental demyelination figures and axonal organelle accumulation were relatively rare. Unmyelinated fibers were also notably damaged in most cases. There was moderate reduplication of endoneurial vascular basement membrane.