Intraosseous epidermoid cysts are rare. A 47 year-old male was seen on October 26th, 1995, complaining of pain and swelling of his left thumb. Thirty years previously, he had sustained an injury on the ulno-palmar side of the distal phalanx of the thumb. He had been shown to have a radiolucent area in the distal phalanx at another clinic, two years prior to visiting our hospital. He had suffered from pain and noticed swelling of the tip of the thumb for two months before presentation. Physical examination revealed a clubbed finger with local tenderness and a small scar. Roentgenogram showed a round radiolucent lesion with expansion and destruction of the cortex. The tumor was encapsulated and filled with atheroma-like material. Microscopically, the cyst wall consisted of stratified squamous epithelium. The cyst was filled with horny material arranged in laminated layers. We surmise that the past trauma is implicated as the cause of this condition, and highly proliferative tissues of the finger tip were implanted into the distal phalanx. On roentgenogram it is very difficult to distinguish an epidermoid cyst from other intraosseous tumors or tumorous conditions.