An investigational muscarinic antagonist, solifenacin is indicated in the treatment of overactive bladder. Solifenacin works to decrease bladder activity by inhibiting contraction of the smooth muscle wall surrounding the bladder. Micturition normally occurs following stimulation of acetylcholine muscarinic M3 receptors within the detrusor muscle wall. As a potent and selective muscarinic receptor antagonist, solifenacin acts specifically at the M3 receptor site. Initial data have shown solifenacin to be more bladder-selective than its predecessors. It is this selective mode of action that gives solifenacin the potential to limit commonly experienced anticholinergic side effects. These developments could translate into higher patient compliance with the potential for better long-term results. Solifenacin has been shown to have a favorable risk/benefit ratio. At a once-daily oral dose of 5 mg/day, clinical data have shown solifenacin to be effective in reducing the symptoms of overactive bladder, with an incidence of dry mouth comparable to that associated with placebo. Results from phase I, II and III clinical trials have shown solifenacin to have a promising efficacy and safety profile for the treatment of overactive bladder. Comparative clinical trials are now needed to determine whether these initial results can prove solifenacin to be more beneficial than other commonly administered antimuscarinics.