Since 1977 we have operated on 13 of 15 triphalangeal thumbs in nine children (five boys, four girls). Follow-up ranged from 22 to 134 months (mean, 65 months). Total active motion averaged 63 degrees at the interphalangeal joint and 79 degrees at the metacarpophalangeal joint. There was no evidence of instability or laxity of ligaments. Reduction osteotomy was insufficient to shorten grossly long thumbs of two patients, and it was necessary to shorten the metacarpal. Premature closure of the phalangeal physis occurred in two thumbs but did not result in inadequate length; one postoperative pin-tract infection resulted in nonunion that required reoperation. This long-term experience supports reduction osteotomy for triphalangeal thumbs because it addresses the deformities and preserves both motion and stability.