BACKGROUND: Differences in the biology, natural history, and treatment results of hepatocellular carcinoma (HCC) in children and adults were sought based on the literature and experience resulting from SIOPEL 1 trial. PROCEDURE: In the SIOPEL1 study, 40 children with HCC were registered from January 1990 to February 1994. Outcome was analyzed in 39. In most cases, disease was advanced at diagnosis: 31% had metastases and 39% had extrahepatic tumor extension and/or vascular invasion. More than 50% of patients had multifocal tumors; 39% of tumors were associated with hepatic cirrhosis. All, but two patients, received preoperative chemotherapy (PLADO--cisplatin and doxorubicin). Outcome, response to treatment, and prognostic factors were analyzed using the SAS statistical package. RESULTS: Overall survival (OS) at 5 years is 28% and EFS is 17% at median follow-up of 75 months (49-90). Partial response to chemotherapy was observed in 18 of 37 cases evaluated (49%). Complete tumor resection was achieved in 14 of the 39 patients (36%). Twenty (51%) never became operable. Multifocality of the tumor, presence of metastases, and PRETEXT grouping adversely influenced OS. A large number of "de novo" HCC cases, fairly high response rate to preoperative chemotherapy (49%) and 54% survival after complete resection constitute a significant difference in comparison with adult HCC series. CONCLUSIONS: Survival for pediatric HCC patients is below 30%. Radical tumor resection remains the only chance for survival. New multi-center prospective studies in children with HCC are required to better results and to allow further study of differences between adult and pediatric HCC should they exist.