The results of clinical, electrophysiologic, and histologic studies in three patients with a type of diabetic peripheral neuropathy, subacute proximal diabetic neuropathy (diabetic amyotrophy), are presented. On the basis of our findings, we suggest that diabetic amyotrophy is a clinical and pathologic entity separate from mononeuritis multiplex. These patients have a generalized neuropathy, and it is postulated that disordered neuron-axonal metabolism forms the basis for the pathologic and clinical changes. Histochemical changes in the muscle biopsy showed type 1 predominance. We suggest that this phenomenon represents a conversion of surviving fibers of whatever type, to a type 1 oxidative metabolism because of the change in use of these fibers.