Brachial plexus neuropathy is an acute neurologic disorder characterized by pain, weakness, and atrophy of the muscle groups affected. Although well documented in the adult literature, relatively few cases have been reported in children. Despite the lack of knowledge concerning its etiology, and lack of an effective therapy, the long-term prognosis is excellent. It is perhaps for these reasons that spinal fluid analysis is not routinely performed during the acute phase of this illness. An evaluation of the clinical course of three children, together with epidemiologic data, suggests that early lumbar punctures and an extensive search for an infecting viral agent, notably coxsackievirus B, are warranted.