From November to December in 2006, we experienced 4 pediatric cases with an elevation of the serum transaminase levels accompanied by acute gastroenteritis. All examined stool specimens were norovirus positive according to the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) assay. The clinical courses of these cases were the same as those of common gastroenteritis. Blood examinations showed only a slight elevation of the transaminase levels at the onset of gastroenteritis, while the symptoms were severe. Interestingly, the transaminase levels significantly increased after gastroenteritis disappeared. The average period between the onset of gastroenteritis and the peak of transaminase levels was 13.8 days. In all cases, the patients were treated with the administration of glycyrrhizin, and the transaminase levels returned to normal approximately 4 weeks (average 26.8 days) after the onset of gastroenteritis, thus suggesting that an elevation of the transaminase levels in association with norovirus gastroenteritis may therefore be a self-limited process which may demonstrate a relatively good natural prognosis. Norovirus is one of the important pathogens which cause an elevation in the serum transaminase levels in young children. When an elevation in the transaminase levels in association with gastroenteritis is observed in young children, it is important to continuously follow up such patients even after the gastroenteritis has disappeared and to perform a virus search based on examinations of stool specimens using an RT-PCR assay in order to detect the presence of norovirus infections.