Peculiar congenital defects of the ossicles may be seen in stapes surgery. These deformities pose a special problem in treatment. The defect may involve all ossicles or only one, for example, the stapes; and malformations of the external ear may or may not be found with such lesions. Only recently has congenital conductive deafness in the presence of a normal external ear been well understood, for hearing loss in these defects has at times been confused with the hearing loss of otosclerosis. In this report, therefore, one variety of these anomalies is presented with its treatment; this particular variety is designated as absence of the oval window. Developmental Considerations Attention in this defect is specifically directed to the development of the oval window and the stapes. Abnormalities in fetal differentiation may result in varying degrees of footplate fixation. Deformity of the footplate may vary from the extreme of mild peribasilar