This study looks at disease diversity, location of lesions, and progression of neuralgic amyotrophy (NA). Forty patients (28 male and 12 female, age range 15 to 70 years) were clinically examined. Muscle atrophy, weakness, and sensory impairment were assessed. Needle EMG and conduction velocities were performed. Careful clinical, electrophysiological, laboratory, and radiological studies excluded other illness. Twenty-two patients were followed for 2 years. Antecedent fever and upper-respiratory tract infection was seen in 22 cases. Pain of sudden onset was always the initial symptom, followed by weakness, mainly in the proximal muscles of shoulder. The affectation was bilateral in 7 cases. Seven cases had a recurrent form of the disease. Clinical and electrophysiological findings suggest axonal lesions of the peripheral nerves, occurring singly (mononeuritis) or in various combinations (mononeuropathy multiplex). Unusual features, such as VII and XI cranial nerves, phrenic nerve, and lateral antebrachial cutaneous nerve affectation, were found. Follow-up showed good function recovery at variable times, even in 1 case with associated myotonic dystrophy (MD). NA is a well-defined entity, with variable clinical expression and data consistent with mononeuropathy or mononeuropathy multiplex, axonal in type. The overall prognosis is good. The progression in a patient with MD suggests that the capability of muscle fiber membrane to accept regenerating nerve sprouts remains in dystrophic muscles.