Various bone lesions in 15 cases of [See Table in the PDF File] Gardner's syndrome in 2 families are reported. Osseous lesions are benign osteomatosis consisting of dense bony proliferations of various size from slight localized thickening to large protuberant masses. The abnormalities appeared variable by location and general bony type. Localized cortical thickening in the long tubular bones is the most common lesion. Protuberant and usually lobulated osteomas of the mandibular angle are a characteristic of Gardner's syndrome. The youngest patient with bone lesions in our series was an 8 year old boy. The bone lesions may precede the appearance of intestinal polyposis and may be an early sign of this disorder. Therefore, in the younger children of a family manifesting Gardner's syndrome, careful and frequent follow-up studies are essential, even though original or early studies were negative.