A ease of infantile carcinoma of the head of pancreas specifically diagnosed as pancreatoblastoma was presented in a 4-year-old Korean boy. A well encapsulates intra-abdominal mass was found which was attached to the ventral aspect of the pancreatic head, covered by the lesser omentum anteriorly, and was predominantly cystic. Histologic examination revealed that the tumor was made up largely of cuboidal to low columnar epithelial cello arranged in acinar or tubular structures and solid sheets, and of a few islands of squamoid cells with elongated nuclei arranged in a parallel fasciculating pattern (squamoid corpuscles). Ultrastructural examination of the acinar or tubular strictures stowed microvilli on the luminal surface, well developed granular endoplasmic reticulum, and electron dense zymogen-like granules especially at the apical portion of the cytoplasm. The tumor cells of squamoid corpuscles had tonofilaments and few zymogen-like granules. These findings strongly support the view that pancreatoblastoma arises from cells which might ultimately differentiate into exocrine acinar cells of the pancreas.