Injuries to the extensor mechanism include a wide range of injuries from minor one to massive defect. And the methods of treatment must be individualized according to the anatomical site, extent and chronicity of injuries. The extensor mechanism is a triangular thin sheet like structure, the function of which cannot be explained completely by the Tubiana's church-steeple like diagram. Authors think that the extensor mechanism should be repaired or reconstructed as a triangular sheet. The tension of the repaired or reconstructed tendon was estimated as good when the neutral extensions were obtained in all the MP, PIP and DIP joints after the completion of sutures. Also authors think that stable sutures are mandatory for the early rehabilitation postopoeratively. Seventy-five patients have been treated by the authors from 1982 to 1994. According to zonal classification, forty-two patients were injured in Zone I. 5 in Zone II, 21 in Zone III, 5 in Zone IV and 2 patients were unclassified due to massive defects of the extensor mechanism. Mostly bony mallet injuries were treated by open reduction and K-wire fixation. Acute tendinous mallet injuries were treated by conservative splinting and old injuries were treated by anatomical plication of the terminal extensor tendon. Old buttonhole deformities were generally treated by the central tendon plication. Massive defects were managed by skin coverage and reconstruction of the extensor mechanism by using a tendon graft which was tailored like a triangular thin sheet. With author's treatment principles, excellent or good results were obtained in about 87%. Consequently, authors emphasize that an anatomical repair or reconstruction is a keystone in the treatment of injuries to the extensor mechanism.