PURPOSE: To review the result of bony mallet finger treated with a closed reduction using extension block K-wire MATERIALS AND METHODS: Between January 2001 and November 2002, among the patients with bony mallet finger underwent closed reduction using extension block K-wire, we retrospectively reviewed 14 patients with 14 fractures who had a minimum follow-up of 12 months. RESULTS: There were 10 men and 4 women, with an average follow-up for all cases 15.7 months (range, 12 months~18 months). According to Crawford's evaluation criteria, we obtained 7 excellent, 5 good, 2 fair. We obtained bony union in all patients, with no remained pain. The average ROM was 67 degrees at postoperative 12 months. Postoperative complications occurred in two cases, which were nail deformity and mild osteoarthritis at the distal interphalangeal joint. There was no pin site infection. CONCLUSION: This technique is not only easier but also less invasive than other techniques for reduction of mallet finger. Also, it shows excellent result with lower complication rate. So, it seems a reliable treatment for bony mallet finger.