Chemotherapy is the only effective method of treating unresectable hepatoblastoma. Most protocols require the administration of multiple highly toxic agents. We evaluated the ability of single-agent high-dose cis-platinum (HD-CDDP) to shrink unresectable primary hepatoblastoma to allow resection. Seven children aged 11 to 72 months had unresectable hepatoblastoma based on size and location. Initial alpha-fetoprotein (AFP) levels were between 4,900 and 1,840,000 ng/mL (mean, 555,900 ng/mL). Chest computed tomography (CT) scans obtained before beginning HD-CDDP therapy showed multiple or bilateral lung masses in 3 patients. Chemotherapy for each of the 7 children consisted of only HD-CDDP, 150 mg/m2, at 3-week intervals. HD-CDDP was stopped and prompt resection performed when AFP levels ceased to decline significantly (n = 4; mean nadir, 18,600); the corrected creatinine clearance decreased below 60 mL/min (n = 2); or, in one case, significant hemorrhage occurred within the tumor. Therefore, the number of HD-CDDP doses given preoperatively varied between 1 and 7 (mean, 3). No children required dialysis. Tumor cells in the bone marrow of one child disappeared completely after one dose of HD-CDDP. Follow-up CT scans showed complete resolution of the pulmonary metastases in 2 children, a partial response in the third, and a marked reduction of primary tumors to resectable sizes. Six children underwent tumor excision with adequate margins; parents of the seventh child refused permission for surgery. There were 2 operative deaths, 3 deaths due to local or distant disease, and 2 patients survived (postoperative follow-up, 22 and 14 months).(ABSTRACT TRUNCATED AT 250 WORDS)