Neurological and neuromuscular disorders are frequent complications in patients with neoplasms and may involve the neuromuscular system, including motor and sensory nerve cell bodies, axons, myelin, neuromuscular transmission and muscle alone or in combination. Electrophysiological studies are of value in delineating the type, degree and extent of involvement, and may be of assistance in pointing towards the underlying cause: paraneoplastic factors, treatment with chemotherapy or radiation or metastatic infiltration. Though some electrophysiological features may be characteristic of certain syndromes, they rarely can stand alone but require clinical, pathological, radiological, and laboratory studies to obtain a diagnosis. Even in cases where such studies are obtained, a final diagnosis may only be ascertained during follow up, since the neuromuscular disorders frequently occur before the neoplasm is detected.