Capsaicin is known to be neurotoxic for C-fiber afferents. We investigated the intravesical application of capsaicin in the treatment of detrusor hyperreflexia (DH) in seven patients (ages 23-52) with neurologic impairment. The patients were evaluated with both ice-water cystometry and formal video-urodynamic studies. Four biweekly courses of intravesical capsaicin treatment were administered using increasing concentrations (100 microM, 500 microM, 1 mM, and 2 mM). Treatment effect was monitored using a bladder diary and urodynamic evaluation one month after capsaicin treatment. Prior to treatment, six of the seven patients demonstrated a positive ice-water test and DH. Two patients were not able to complete the study due to discomfort attributed to capsaicin. Five of the seven patients completed the four courses of increasingly concentrated capsaicin. Three patients noted symptomatic improvement while two did not. The mean urodynamic bladder capacity significantly increased from 124 +/- 39 ml pre-capsaicin to 231 +/- 62 ml one month post-capsaicin in the three patients with symptomatic improvement (p < 0.05). Urodynamic testing revealed that one of the six patients with a positive ice-water test lost that response after intravesical capsaicin. Intravesical capsaicin is a novel and promising treatment for detrusor hyperreflexia in neurologically impaired patients.