Sixteen pediatric radial mononeuropathies were seen among 2077 electromyograms performed in the electromyography laboratory at The Children's Hospital, Boston, during 16.5 years, 1979-1995. Eight (50%) of these radial neuropathies, including 2 in newborns with apparent prenatal onset, were atraumatic, primarily related to compression in 6 and entrapment in 2. The other 8 (50%) were traumatic related to fractures or lacerations. Electromyography documented the radial neuropathy to be localized to the proximal main radial nerve trunk in 2 (13%), distal main radial nerve trunk in 9 (56%), and posterior interosseous nerve in 5 (31%) children. Significant improvement was noted in 13 of the 16 radial neuropathies--within 6-12 weeks for demyelinating lesions and up to 17 months for axonal injuries. Rarely, a child with a chronic progressive radial neuropathy or a postfracture radial neuropathy that does not improve in 3 months may require exploration.