To determine the extent of progress in the treatment of sacrococcygeal teratomas (SCTs), we evaluated the experience with 73 patients over 40 years. The medical records of the children were reviewed for demographics, histology, clinical course, and outcome. Therapy differed depending on the type of SCT, histology, and decade of diagnosis. The female:male ratio was 4.2:1 and did not vary significantly with the histology of the tumor. Fifty-seven patients presented with benign disease. There were five recurrences in this group, only one of which did not have an initial coccygectomy. One tumor, originally thought to be benign with immature elements, had a local recurrence at 7 months, 10 months, and 16 months after the original operation and was discovered to have embryonal carcinoma with nodal involvement. This child was treated with chemotherapy and is disease-free at 7 years. Morbidity in the benign group included 3 postoperative wound infections. Three infants died, one before operation with beta-hemolytic Streptococcus sepsis. Two neonates died in the early postoperative period, one on day 1 with a ruptured subcapsular hematoma of the liver, and the second on day 2 with disseminated intravascular coagulation/sepsis. Benign SCT occurs at a younger age than malignant tumors. The average age of presentation of benign tumors is 20 days versus 468 days in children with malignant disease. The technique of wide resection of benign lesions with coccygectomy is helpful in preventing recurrence and has changed little over the last four decades. Malignant SCT occurred in 16 children (22%).(ABSTRACT TRUNCATED AT 250 WORDS)