Diabetes is the most common cause of peripheral neuropathy in the world. More than half of patients with diabetes have neuropathy, and half of patients with neuropathy have diabetes. Diabetic neuropathy is a major cause of disability and health care expense. This article reviews the various forms of diabetic neuropathy with a focus on diagnosis and treatment.Diabetes causes a wide variety of peripheral nerve problems. These can be divided into chronic neuropathies, of which distal symmetric polyneuropathy is the most common, and acute neuropathies, such as diabetic amyotrophy. There is growing evidence suggesting that prediabetic levels of hyperglycemia and other consequences of obesity and dyslipidemia contribute to neuropathy risk. Evolving literature suggests that many of the acute diabetic neuropathies are related to inflammatory mechanisms. An important exception is treatment-related neuropathy, previously known as "insulin neuritis".While disease-altering therapy continues to prove elusive, our understanding of basic disease mechanisms is improving, and new diagnostic and research tools will hopefully lead to novel therapies for distal symmetric diabetic polyneuropathy.