We report a 2-year-old girl who demonstrated "benign convulsions with gastroenteritis (CwG)" with transient splenial lesions twice during the winter. The first episode was associated with noro-virus and the second with rota-virus. During each episode, seizures occurred in clusters without clinical signs of dehydration, hypoglycemia, electrolyte derangement or cerebrospinal fluid abnormalities, and her consciousness was clear during the interictal period. Those findings were consistent with CwG. As transient splenial lesions were not accompanied by any neurological abnormalities other than seizures, she was not diagnosed as having encephalopathy, but as having CwG. Diffusion-weighted magnetic resonance imaging of the brain demonstrated hyperintense lesions in the splenium of the corpus callosum, which disappeared within a week. We speculate that CwG is likely to lead to transient splenial lesions.