OBJECTIVE To study the classification and individualized treatment of the terminal phalanx of thumb duplication. METHODS From Apr. 2003 to Dec. 2012, 76 patients with 77 involved thumbs duplication at the level which is distal to the interphalangeal joint were retrospectively studied. Based on the morphology (the nail width and the thumb circumference) and the deviation of the thumb, we classified the terminal phalanx of thumb duplication into 5 types as Type A (no bony connection called floating thumb), Type B(asymmetry and no deviation), Type C(asymmetry and deviation), Type D (symmetry and no deviation) and Type E(symmetry and deviation). Different surgical procedures were selected according to different types. Simple excision of the smaller thumb was adopted for Type A case. Removement of the smaller thumb (usually the radial) and of the collateral ligament of the interphalangeal joint were selected for Type B. Removement of the smaller thumb (usually the radial) and reconstruction of the collateral ligament of the interphalangeal joint, as well as corrective osteotomies at the neck of the proximal phalanx were performed for Type C. The modified Bilhaut-Cloquet procedure with reconstruction of the collateral ligament of the interphalangeal joint were adopted in Type D. The classical Bilhaut-Cloquet procedure, or the modified Bilhaut-Cloquet procedure with reconstruction of the collateral ligament of the interphalangeal joint and corrective osteotomies at the neck of the proximal phalanx were performed in Type E. The results were assessed by an evaluation form for thumb duplication by the Japanese Society for Surgery of the Hand. RESULTS According to our new classification standard, there were 3 cases with Type A duplicated thumbs, 36 with Type B, 13 with Type C, 15 with Type D, 10 with Type E. All the 76 patients underwent the individualized surgical treatment. The patients were followed up for 6-60 months. According to the evaluation form, excellent results were achieved in 66 thumbs, good in 9 thumbs and fair in 2 thumbs. CONCLUSIONS The new classification could comprehensively describe the clinical features of the terminal phalanx of congenital thumb duplication. Individualized therapy, including basic and repeated surgical procedure could be adopted for each type with satisfactory results.