We made a prospective study of 208 patients with tibial fractures treated by reamed intramedullary nailing. Of these, 11 (5.3%) developed dysfunction of the peroneal nerve with no evidence of a compartment syndrome. The patients with this complication were significantly younger (mean age 25.6 years) and most had closed fractures of the forced-varus type with relatively minor soft-tissue damage. The fibula was intact in three, fractured in the distal or middle third in seven, with only one fracture in the proximal third. Eight of the 11 patients showed a 'dropped hallux' syndrome, with weakness of extensor hallucis longus and numbness in the first web space, but no clinical involvement of extensor digitorum longus or tibialis anterior. This was confirmed by nerve-conduction studies in three of the eight patients. There was good recovery of muscle function within three to four months in all cases, but after one year three patients still had some residual tightness of extensor hallucis longus, and two some numbness in the first web space. No patient required further treatment.