Twelve ataxic subjects (seven with Friedreich's heredo-ataxia and five with a cerebellar vascular or traumatic lesion) were examined by way of urodynamic evaluation. The results explain the role the cerebellum plays in the modulation of the micturition reflex and confirm the importance of bilateral encephalic damage in causing vesico-sphincteral malfunctioning and the important role of the lateral myelon cords in transporting bladder proprioceptive sensitivity.