Purpose : This study was conducted to analyze the clinical materials and treatment results of 13 cases of subungual exostosis. Materials and Methods : Thirteen subungual exostoses of the foot treated from January 1991 to December 1997 were studied. We analyzed the clinical data and results of treatment to identify the clinical characteristics of this disease. We investigated the location, shape and relation of exostosis to phalanx with simple x-ray of the foot to identify the radiological characteristics. All the cases were sent to pathologic examination after resection to determine the pathological characteristics. Results : The results of physical examination on presentation were various. Most cases were located at the dorsomedial side of the distal phalanx and were involved in the toe nail. Eleven cases were located at great toes and one each at the 2nd and 3rd toe. Causes of exostosis were not clear, but 2 cases were related to trauma. For the type of exostosis, 7 cases were sessile and 6 were stalk type. On histologic examination, 9 cases showed a cartilaginous portion with overlying proliferating fibrous tissue and underlying bone formation. There was a gradual maturation of spindle cell proliferation from cartilage to cancellous bone. The cartilage was moderately cellular with some pleomorphism, but true anaplasia was not present. Conclusion : The clinical presentation and findings of simple x-rays were most helpful in diagnosing subungual exostosis. Complete excision of the mass achieved complete relief of symptoms and recovery without recurrence in all cases.