Tight junctions play a critical role in the maintenance of the urine-blood barrier creating a physiological barrier to the passage of ions and solutes between the urine and blood. Alterations in this urine-blood barrier function have been demonstrated in some diseases and regulation of the tight junction function has been recognised as an important aspect of the cell biology of cancer in terms of disease progression and as a potential therapeutic target. Although tight junctions play an important role in the physiological control of bladder function, there is little published on their molecular composition or regulation in the normal or diseased bladder. The purpose of this review is to summarise current understanding on the role and regulation of tight junction function in the normal and diseased bladder.