The influence of extrinsic innervation on bladder wall tension (tonus) and on intravesical pressure patterns was studied with a new cystometric procedure (Controlled Slow Cystometry, CSC) and during natural filling. After parasympathectomy, but not after sympathectomy, the basal intravesical pressure was markedly increased. At low filling rate the partial or completely denervated bladder was filled from small initial volumes without any increase in intravesical pressure. At higher rates of filling a pressure rise occurred, and this reaction was not affected by either parasympathectomy or sympathectomy. As in the intact cat, the new pressure level was retained when the filling rate was gradually reduced. The various intravesical pressure patterns observed during filling were preserved in the partial or completely denervated organ. Thus, bladder adaptation during natural filling occurs independently of extrinsic innervation.