Two cases of incomplete regression of ventral mesogastrium were reported. Their nomenclature, etiology, symptoms and characteristic roentgenologic findings were discussed in relation to anatomical study. Because of its unique etiology and symptoms, charecteristic roentgenologic findings, and effectual remedy, it is suggested that this disease should be distinguished from "abnormal adhesion of fibrous bands" as an independent anomaly called incomplete regression of ventral mesogastrium. The roentgenological findings were: An incisure was found in the upper portion of pars descendens duodeni. It sank deeply and reduced two thirds of the normal diameter of the intestinal lumen to form an eccentrie intestinal stenosis. The intestinal lumen, near the inner border of the incisure was smooth, and there was no sign of serrated image formed by intestinal mucosa. The part of intestinal lumen was not distended in hypotonic radiography. All the above signs were caused by the traction and binding of the nonregressed mesogastrium.