PURPOSE Capsaicin was used to treat symptomatic patients with hyperactive or hypersensitive bladders. MATERIALS AND METHODS Capsaicin solution (1 mM.) was instilled into the bladder of 16 patients with spinal hyperreflexia, bladder instability or hypersensibility. RESULTS Frequency decreased in 14 patients and continence was achieved in 10 of 14 incontinent cases. Mean first desire to void and maximal cystometric capacity increased significantly. These effects lasted for 6 to 12 months and were renewed following repeat treatment. CONCLUSIONS Bladder afferent desensitization with capsaicin is promising in patients with motor or sensory bladder dysfunction, although initial pungency might limit its use.