Hepatoblastoma, a malignant hepatic tumor in children, is thought to be an embryonal tumor resulting from developmental disturbances during organogenesis. Although factors that might be involved in the tumorigenesis have been suggested, an association between hepatoblastoma and the patient's birth weight has not been reported. We have accessed the data in the Japan Children's Cancer Registry and have analyzed patients' diagnoses and birth weights. During the 9 years from 1985 to 1993, 38 (0. 38%) patients with tumors who weighted less than 1500 gm at birth were identified among 9923 registered patients. Hepatoblastoma was diagnosed in 9 patients of very low birth weight, representing 3. 9% of the 231 patients with hepatoblastoma registered. A significant linear trend toward an increase in the percentage of patients with a birth weight of less than 1500 gm was observed specifically in hepatoblastoma (p = 0. 0047). The percentage rose from 0. 7% (1/138) in the 5-year period of 1985 to 1989 to 8. 6% (8/93) in the next 4-year period (1990 to 1993). This increase was attributed to the significant increase in the percentage of patients who weighed less than 1000 gm at birth (p = 0. 0028). A separate peak in the number of patients in the birth weight range of less than 1000 gm suggests that the cause of hepatoblastoma related to very low birth weight may be different from that of other patients. Full analysis of the patients' data is an urgent matter VSports手机版. .