We performed electrophysiological studies on both legs of 52 children, aged from 3 months to 15 years, with idiopathic club foot. In only nine (17%) was no abnormality found. Isolated peroneal nerve damage was seen in 14 (27%). Abnormality of both peroneal and posterior tibial nerves was found in five (10%). Four patients (8%) had evidence of isolated spinal-cord dysfunction, whereas combined spinal-cord and peripheral-nerve lesions were seen in 14 (27%). Six patients (11%) had variable neurogenic electrophysiological patterns. In 13 patients in whom the studies were repeated neither progression nor improvement of the electrophysiological parameters was observed. Pathological electrophysiological findings were found in 66% of conservatively-treated patients. In the 43 patients treated surgically, all 16 with fair and poor results had pathological electrophysiological findings and 12 required further operations. Multiplicity of the pathological findings was related to the severity of the deformity of the foot; normal studies represent a good prognostic sign. Electrophysiological studies are useful in idiopathic club foot with residual deformities after conservative or operative treatment. Our findings support the theory that muscle imbalance is an aetiological factor in idiopathic club foot.