Anal endosonography using a specially designed hard cone attachment to a radial 7-MHz probe has been performed in 26 normal patients -3 patients following lateral anal sphincterotomy, 1 patient undergoing electromyophysiological mapping of the external and sphincter, and in 2 resected specimens. The examinations were rapid, simple, and well tolerated, and they provided high-resolution images of the five layers of the anal canal: mucosa, submucosa, internal and sphincter, intersphincteric plane, and external anal sphincter. Views of the ischiorectal fossa were limited. The configuration of the anterior part of the external anal sphincter differed between males and females.