From 1941 through 1983, a total of 66 patients with sacrococcygeal teratoma were seen, representing 41 percent of the total of 162 patients with teratomas from all anatomic sites seen over this period. Forty-six (70 percent) of the patients with sacrococcygeal teratomas were female and 34 (52 percent) were neonates. Younger patients had a significantly better prognosis. Approximately half (48 percent) of the patients had benign tumors. Of the other 34 patients, 19 (29 percent) had frank malignancy, being either a purely malignant tumor or a tumor with malignant mixed with benign elements, and 15 (23 percent) patients had tumors containing embryonic but no malignant components. Patients with tumors containing mature adult or embryonic tissues have a good prognosis. However, malignant sacrococcygeal teratoma portends a bleak prognosis irrespective of therapy (in this series only one patient survived among 19 patients with an average survival of 16 months after diagnosis).