On the 10th day of pregnancy, the mother rats were injected with water miscible vitamin A (200,000IU/kg) intraperitoneally to gain fetuses with malformed ear induced by maternal hypervitaminosis A. Their fetuses were removed on the 21st day for preparation of their skeletal specimens by using bone and cartilage staining. In order to examine pathological findings of the malformed ear, chiefly of the middle ear region, a stereoscopic microscope was used. The results were as follows: No abnormalities were found in the majority of the tympanic bone, Meckel's cartilage and malleus. Abnormalities such as malformation and absence were found in the majority of the styloid process from Reichert's cartilage origin, the incus and the stapes. In view of the above phenomena, these are highly probable that the malleus has its origin in the first branchial arch that is associated with the Meckel's cartilage and the stapes has its origin in the second branchial arch that is associated with the Reichert's cartilage. It is also probable that the greater part of the incus also has its origin in the second branchial arch.