Polyneuropathy is any disease process affecting the function of or causing damage to multiple nerves of the peripheral nervous system. There are numerous etiologies of polyneuropathy, most of which are systemic and the most common of which is diabetic neuropathy. The clinical presentation varies by etiology as well as classification of the polyneuropathy, but generally manifests as sensorimotor disturbances (pain, paresthesia, numbness, weakness, and loss of coordination and balance), which have a gradual onset and progressive course. Distal nerves are affected most commonly, but the disease process may progress proximally with time or progression of the underlying etiologic disease entity. Diagnosis is made clinically, but laboratory studies, electrodiagnostic testing, and/or nerve biopsy may be required in some cases. Management varies depending on the etiology.