The authors present a case of extension loss of great toe caused by entrapment neuropathy of a peroneal nerve due to an osteochondroma of the proximal fibula. Plain radiographs revealed no bony abnormality around the foot or ankle, but a sessile exophytic bony growth at the proximal fibula. A positive Tinel sign in this area led us to a suspicion of compressive neuropathy of the peroneal nerve, and a subsequent electrophysiologic study confirmed the entrapment neuropathy. The peroneal nerve was decompressed by excisional biopsy. At 3 months postoperatively, normal full extension of the great toe was completely restored. The current case deserves attention in that the only clinical manifestation of peroneal nerve entrapment neuropathy by the osteochondroma at the fibular neck was extension loss of great toe.