A clinical study was performed on the 26 cases of patients treated by operation for mallet finger at Yonsei University Severance Hospital from January 1988 to December 1991. There were eight patients with a small avulsion chip fracture, ten patients with the intraarticular fragment with volar subluxation, and four patients with fragments involved more than two-thirds of the articular surface. Of the 26 cases seven were treated with a pin and pull-out wire, six were treated with tuckling or shortening of terminal tendon. Seven fingers had more than one surgical procedure. There were eight good results. Seven patients had very little active extension and the result was classified as poor. In the treatment of older injuries, especially in the delayed cases, reefing of the extensor tendon and immobilization of the distal joint with a Kirschner wire seems to give the highest percentage of satisfactory results. The tuckling or shortening procedure of terminal tendon was good in neglected mild degree mallet fingers. Complications occured in eight cases. In three of these there was superficial skin necrosis. In the one other case, premature closure of epiphysis occurred at the distal phalanx.