Adamantinoma of long bones is a rare primary bone tumor. Approximately 100 cases have been reported in the literature. In the fourteen cases we studied in detail the ages of the patients ranged from thirteen to sixty-seven years and there were as many males as females. Twelve of the lesions were located in the tibia and two, in the humerus. The roentgenographic findings were sharply defined eccentric lobular lesions in the diaphysis. Some of the lesions were lytic and coarsely trabecular with a honeycomb appearance occasionally associated with periosteal new-bone formation. A sawtooth area of cortical-bone loss was found to be characteristic of this lesion. A microscopic finding is presented to support the theory of angioblastic origin of this tumor. The most successful treatment was amputation. Less often en bloc excision succeeded. Metastases to other bones, regional lymph nodes, and the lung were recorded.