We performed urological evaluations in 18 patients with the tethered spinal cord syndrome. Of the patients 4 had low grade vesicoureteral reflux but none had significant upper tract anomalies. Urodynamic studies documented a flaccid bladder in 9 patients (5 with supersensitivity to bethanechol), an uninhibited bladder in 5, mixed bladder dysfunction in 2 and normal function in 2. Repeat urodynamic studies were performed in 15 patients at least 6 months after release of the tethering. Of 8 patients with flaccid bladders studied postoperatively 6 had significant changes: 2 became normal, 2 had limited contractions and 2 had evidence of upper motor neuron abnormalities. Supersensitivity to bethanechol was of no predictive value. All 4 patients with uninhibited bladders who were evaluated preoperatively and postoperatively had improved and 3 currently are entirely normal. Careful urological evaluation of patients with the tethered spinal cord syndrome is helpful not only for diagnosis but also for appropriate management preoperatively and postoperatively. The fact that lower urinary tract function improves in some patients should encourage early and aggressive neurosurgical management of patients with this syndrome.