Selective neurotomies or alcoholization of a limited number of sacral roots or of an unilateral section of nervi erigens was carried out in 21 patients presenting an incomplete upper motor neuron lesion. These patients suffered from urinary incontinence due to detrusor hyperactivity. Some of these patients were retaining a large amount of residual urine as a consequence of sphincter spasm. The localization of the roots involved in the spastic process was made by differential anesthetic sacral blocks through a needle introduced into the posterior sacral foramina. Results of blocks were controlled by cystometry and uroflowmetry. According to localization either alcoholization or section of 1–3 sacral roots were performed. When a perfect lateralization was present, as in hemiplegic patients, a unilateral section of nervi erigens gave good results. This approach has been utilized in 26 patients with encouraging results.