Objective To examine the safety,efficacy and t olerability of tolterodine in randomized,doubled-blind,3weeks study of patients with idiopathic overactiv e bladder(IOAB).Method Study compared tolterodine(lmg )to oxybutynin(5mg )and placebo taking 2hour before going to bed at night.Changes in micturition diary variables were evaluated after 3weeks' treatment.Result Both tolterodine and oxybutynin significantly decrease d the number of micturiton /lh from baseline,compared to placebo.The most common adverse effect was dry mouth.Tolterodine was tolerated significantly better than oxybutynin when dry mouth(both frequency and intensity)were consid-ered.Conclusion Although oxybutynin is highly effective,its clinical utility is limite d by side effect.Patients receiving tolterodine should not experience hese limitations and instead will get safe and long-term effe ctive treatment.