Electrophysiological examination was performed on 50 type II diabetic patients to verify whether insulin secretory reserve is a factor influencing the susceptibility to develop polyneuropathy. The results showed that less significant metabolic derangement related to high insulin secretory reserve, and not the high insulin secretory reserve by itself, may prevent the development of neuropathic disorders. These data are consistent with the current opinion that diabetic polyneuropathy is the consequence of the metabolic derangement caused by chronic hyperglycemia.