Radiographic findings and related information are described for a series of 26 patients from six unrelated families. The tumor complex consists of a presacral teratoma and a sacrococcygeal bony defect occurring in a familial pattern. Many of the patients also had an associated vesicoureteral reflux, skin dimples, retrorectal abscess, and anorectal stenosis. The main radiographic features were the presence of a unilateral or central developmental deformity of the sacrum and coccyx, and the absence of radiographically visible soft-tissue calcifications.