To simply perform a rectal examination is not adequate. The interpretation is of paramount importance. Often in cauda equina lesions, tone found in the sphincteric site will be misinterpreted to mean somatic reflex tone. The tone found in these low lesions with areflexic bladders is caused by the fact that the internal anal sphincters are innervated by the sympathetic fibers, which are still intact in these patients. One may often have to rule out physical tone--an intrinsic property of tissue. When performing the dermatome examination for sensation, it is important that the examiner orders the patient to close his eyes. Then the examiner hits the air only while asking the patient. "Do you feel anything now?" It is surprising how many patients will respond by saying, "I feel it!" These patients do a great deal of wishful thinking or have paresthesias or dysesthesias. If these two factors are not ruled out, the examiner can be misled. The examiner should not stimulate two sites simultaneously (eg, leaning with the elbow on the thigh of the patient while testing the anogenital dermatomes, particularly if sensation is present in the thigh). This error in technique can produce a false-positive response while pinning the anogenital sites, which may be anesthetic. It is unsatisfactory for the examiner to state that the patient has sensation without specifically stating whether it is pinprick, light touch, or even hypalgesic, especially when referring to the sacral segments. Additionally, the examiner must state whether the sensation is unilateral or bilateral. To examine only the perianal dermatomes is insufficient; the penile and scrotal dermatomes must also be examined.(ABSTRACT TRUNCATED AT 250 WORDS)