For more than a decade congenital mesoblastic nephroma of infancy has been recognized as an entity different from Wilms tumor in its clinical and histopathologic features. However, this tumor is sometimes confused with Wilms tumor and consequently, inadvertent and vigorous therapy compatible with that for Wilms tumor is given. we reviewed the literature and analyzed 90 cases of congenital mesoblastic nephroma in the English and Japanese literature. The importance of early and accurate histopathologic diagnosis of the resected specimen to avoid inappropriate post-operative therapy is emphasized, and the peculiar features of congenital mesoblastic nephroma are characterized.