Histological studies were conducted on 4 patients with intestinal atresia due to intrauterine intussusception. This atresia is characterized by a polypoid lesion as the remnant of the invaginated and necrotized intestine in the distal intestinal lumen. As the result of the histological survey in the affected intestine, we tentatively classified this atresia into two types, type A and B. In type A, the polypoid lesion is observed at the blind end, with relatively good preservation of the structure of the intestine. In type B, the polypoid lesion is located apart from the blind end, and the lesion is markedly necrotic. The interruption of intestinal blood flow seemed to be more severe in type B than in type A.