Endosonography from within the anus has been used to image the anorectum and its associated musculature. A 5.0-MHz endovaginal probe was inserted vaginally, and longitudinal and cross-sectional views of the anorectum were obtained. We were able to measure rectal length and diameter, puborectalis thickness and angle, thickness of internal and external anal sphincter, and the curvature of the anal canal. We visualized defects in the internal and external anal sphincters. Suitable images were obtained from 70 subjects. Muscle thicknesses were within previously published ranges. Twenty-five of 70 subjects (36%) had defects of the internal anal sphincter, and 19 of 65 subjects (29%) had defects of the external anal sphincter.