In Japan, an increase in hepatoblastoma with low birth weight has become evident since the 1990 s, and there is concern about a possible increase in unfavorable neuroblastomas after the cessation of mass screening in 2004. The trends in incidence of malignant solid tumors in children younger than 15 years of age were inferred by evaluating registration incidence in the registry of the Japanese Society of Pediatric Surgeons. A significant trend toward an increase in the registration incidence for hepatoblastoma was observed (p<0.001). Hepatoblastomas with low birth weight (<1500 g) represented as many as 16% of hepatoblastomas. In hepatocellular carcinoma, there was a significant trend toward a decrease (p=0.042). The registration incidence of nonmass screening-detected neuroblastoma remained unchanged until 2003, but the registration incidence in the period from 2004 to 2012 was significantly higher than that in the period from 1996 to 2003 (p=0.021). There was an increase in the relative incidence of favorable stages after the cessation of mass screening. The notable increase in hepatoblastoma during the last three decades is partly attributed to an increase in hepatoblastoma in children of low birth weight, but this alone is not sufficient to explain the increase in hepatoblastoma. The increase in neuroblastoma after the halt of mass screening is so minimal that it is not recommended to consider reimplementation of mass screening. Copyright © 2015 Elsevier Inc. All rights reserved.