Polydactyly is the most common congenital anomaly of the upper limb. Polydactyly is classified as preaxial polydactyly(thumb), central polydactyly(index, middle and ring fingers), and postaxial polydactyly(little finger) by the site of the extra digit. A 3-day-old female newborn had a 1.5 * 1.0cm sized flesh color ed pedunculated sac like mass on the proximal phalanx of her right thumb since birth. A roentgenogram on the hand revealed no bony abnormalities of the digit and the mass contained no bony structures. The stalk of the mass was cut by the CO2 laser. On histopathological examination, a cartilage structure was found in the loosely arranged, edematous dermis and the overlying epidermis was flattened. The clinical and histological findings support the diagnosis of preaxial polydactyly. We report this interesting case of preaxial polydactyly with a review of the literature. (Kor J Dermatol 1997;35(2): 379-382)