Continuous measurements were made of bladder blood flow by laser Doppler flowmetry in anesthetized dogs during bladder filling and emptying. In both mucosa and muscle, perfusion was inversely proportional to intravesical pressure. There was significantly greater perfusion in the bladder mucosa of males than females at baseline and up to 10 cm water filling pressure but not in the muscle. Intra-arterial infusion of the nitric oxide synthase inhibitor NG-nitro-L-arginine produced a significant decrease in resting bladder perfusion in the mucosa only, with no differences seen in the response to intravesical pressure. Intra-arterial infusion of L-arginine produced a significant increase in the level of perfusion in the mucosa seen immediately after the bladder was drained. No changes were observed in muscle perfusion after L-arginine. These results suggest that the perfusion of the bladder mucosa differs by gender and is regulated differently than the bladder muscle, possibly related to the different function of the two layers.