The microscopic anatomy of two rectobulbar fistula specimens was studied histologically in serial sections to determine the route taken by the fistulœ and the arrangement of the associated muscles and sphincters. It was found that the sole muscle available for reconstructive sghincter surgery was the levator ani complex, adapted and modified to the visceral ubnormality. In each case, the puborectalis sling was short, aid confluent inferiorly and posteriorly beneath the fistula with the bulbocavernosus muscle. The findings proved to be relevant to the techniques of surgical reconstruction of the anal canal in patients exhibiting this deformity