Diabetes mellitus leads to several recognizable clinicopathologic neuropathic syndromes. Diagnosis and evaluation requires a thorough history and neurologic examination, nerve conductions and needle electromyography (EMG), blood studies, consideration of cerebrospinal fluid analysis, and nerve and muscle biopsy in the most severely affected patients. Microangiopathy is the commonest cause of diabetic neuropathy, associated with potentially reversible metabolic, immunologic, or ischemic injury. Tight glycemic control and symptomatic therapy is beneficial in some patients but does not prevent progression of neuropathy especially in patients with severe motor and gait disability. Intravenous immune globulin is a novel therapy in diabetic patients. It may be considered in selected patients well characterized by clinical, electrophysiologic, histopathologic studies, and one of the following progressive syndromes: mononeuropathy multiplex, primary demyelinating motor or sensorimotor neuropathy, and peripheral nerve perivasculitis or microvasculitis associated with vascular membrane attack complex protein deposits.