The physiology of the muscle systems of the human lower urinary tract is still not known in detail. To study the functional basics of this complex organ system, experiments are often performed in animal models including rhesus monkeys. To apply the results of animal model studies to the humans, a clear knowledge of the comparative anatomy of both species is necessary. However, detailed comparative studies of the lower urinary tract of the rhesus monkey and the humans are lacking. Accordingly, a detailed study on the sphincteric musculature of the lower urinary tract of the rhesus monkey was performed in order to demonstrate anatomical correspondences and differences between both species. The lower urinary tract anatomy was investigated in 18 male and female rhesus monkeys (Macaca mulatta) by serial sections. Immunohistochemical staining methods were used to differentiate striated and smooth musculature. Three-dimensional reconstructions were performed in order to demonstrate the topographical anatomy of the different muscle systems. In both man and male rhesus monkeys, a urethral sphincter muscle exists independent of the pelvic floor musculature, with a smooth and a striated muscular part. A urinary diaphragm (diaphragma urogenitale) does neither exist in the rhesus monkey nor in the human. In contrast to women, a striated muscle encircles the urethra and vagina together in the female rhesus monkey. A vesical sphincter muscle, found in the human bladder outlet, does not exist in the rhesus monkey.