Diabetic autonomic neuropathy (DAN) affects each tissue, organ, system and the whole body, and presents with a diverse clinical picture. Originating from endocrine factors, this neurological disease may cause symptoms, whose differential diagnosis needs a good knowledge of the whole internal medicine. DAN is strongly involved in the development of diabetic foot, ulceration and amputation. The life threatening consequences of cardiac and patient-frustrating sequels of other types of DAN is more difficult to estimate. In this chapter the different clinical aspects of DAN will be discussed, according to the involved system--cardiovascular, gastrointestinal, genitourinary, sudomotor and pupillary dysfunctions and the unawareness and unresponsiveness to hypoglycaemia. The diagnostic tests for DAN are more complicated and time consuming, compared with the somatic tools. There is a need for simple devices and methods for evaluation of autonomic functions in the everyday clinical practice. Tight glycaemic control is the cornerstone of the prevention, progression and retardation of DAN. An effective broad-spectrum pathogenetic treatment of neural deterioration remains to be established. In most cases symptomatic drugs are the treatment of choice.