Intravesical treatment for non-muscle invasive bladder cancer involves the direct instillation of immunotherapy or chemotherapy into the bladder. While this approach limits systemic absorption, patients undergoing this localised treatment frequently report significant urological side effects, including increased frequency and urgency of urination, haematuria and dysuria. A relatively new drug used for bladder cancer is gemcitabine, which has shown an improved efficacy and toxicity profile with comparison to the first-line chemotherapy mitomycin C in patients. Elucidating the effects of gemcitabine on the normal cells and changes in the normal function of the bladder may reveal possible targets for preventing, alleviating or treating the adverse urological effects associated with this treatment. Taken together, the results of this thesis suggest that intravesical gemcitabine induces a painful and overactive bladder phenotype in patients through a combination of enhanced urothelial and inflammatory mediators and altered efferent nerve activity, which may sensitise afferent nerves and reduce detrusor muscle contraction respectively.