A pertinent procedure for preserving postoperative urinary and sexual functions was searched in the radical surgery for rectal cancer, from a neuroanatomical point of view, and the clinical status about disturbances of these functions was analized in relation with a mode of preservation of the lower hypogastric and/or the pelvic nerve among the patinet undergone the surgery applied this procedure. The result of the operation was also evaluated as for the influence of this procedure on the curability of the cancer. Results obtained were as follows: 1. In the anatomical study with 17 necropsy cases, it was found that the most preferable mean for identifying the lower hypogastric nerve, pelvic plexus and pelvic nerve was to begin with isolating the upper hypogastric nerve dividing the posterior peritoneum along the lower abdominal aorta, and to follow the bilateral lower hypogastric nerves on the inner surface of the pelvic cavity down to the pelvic plexus, from which the pelvic nerves were able to explore by the retrograde approach to the sacral foramina. Since this procedure was able to be progressed in accordance with that of the radical operation by Miles, technical troubles were of eliminable. 2. Urinary functions were examined on 47 cases out of 60 patients received the surgery with the nerve-saving procedure above. a) The period before the spontaneous urination occurred after the surgery was prolonged significantly by the bilateral injury to the pelvic nerve and this was not observed in the patient whose pelvic nerve was unilaterally injured, as well as in the patient whose lower hypogastric nerve was uni- or bilaterally injured. b) The result of cystometry and catheterization study showed that cystic hypotonia and urinary retention prolonged as long as 40 days or more, and 23 days in average in the patient with injury to the bilateral pelvic nerves, as compared to 8 days in average in the patient with bilateral denervation of the lower hypogastric nerve and also in the patient with unilateral injury to the pelvic nerve. Duration of sensation as to urinary retention was quite accorded with these results. 3. Sexual function was surveyed making inquiries by the letter to 48 subjects and was summarized on 43 including 19 female with satisfactorily recorded answers. a) Ability of the erection was preserved in about 60 to 70% of the patient regardless of presence or absence of the denervation of the lower hypogastric nerve. However, it was impaired in all patients with bilateral injury to the pelvic nerve, although even the unilateral preservation saved the ability in all. b) Ability of the ejaculation was satisfactorily kept only in the subjects whose lower hypogastric nerve was bilaterally saved. Among those who had injury to bilateral pelvic nerve, only the patient whose lower hypogastric nerve was bilaterally saved preserved the ability, suggesting a close participation of the hypogastric nerve to the ejaculation. 4. The decrease in the curability of the cancer under this procedure was not observed, compared with that in patients undergone the surgery performed without the positive intention to save the nerve but with the aim to eradicate the cancer.