The incidence of autonomic dysfunction as a complication of diabetes mellitus is reported to be as high as 20% to 40%. Symptoms of diabetic autonomic neuropathy (DAN) are often vague, and signs difficult to detect on routine physical examination. The early diagnosis of DAN is possible by utilizing several simple noninvasive tests, which may also be helpful in localizing the lesion(s) to specific autonomic pathways. DAN may affect multiple organ systems, to include cardiovascular, gastrointestinal, genitourinary and/or neuroendocrine, and may, in fact, be life-threatening. The same metabolic disturbances of somatic peripheral nerve may also be responsible for DAN. Like somatosensory neuropathy, definitive therapy for DAN is not yet satisfactory, although multiple chemotherapeutic agents have been tried and warrant further investigation.