Introduction: This multicenter, randomized, double-blind, parallel-group, Phase III, pivotal trial investigated the efficacy and safety of solifenacin succinate 10 mg, a once-daily (OD) oral antimuscarinic agent, in overactive bladder syndrome (OAB). Materials and methods: A total of 634 adult patients with OAB symptoms were randomized to either solifenacin 10 mg (n = 318) or placebo (n = 316) OD over 12 weeks, to examine changes from baseline in micturition-, incontinence-, urgency- and nocturia- episodes/24 hours, measured using a 3-day diary. Results: Solifenacin significantly reduced the mean number of micturition-, urgency- and incontinence-episodes/24 hours at end of treatment (P < 0.001 for all versus placebo); these improvements were observed at 4 weeks, and continued over 12 weeks. Adverse events were generally mild or moderate in severity and typically anticholinergic in nature. Conclusions: Solifenacin 10 mg OD was well tolerated and effective in treating major OAB symptoms, including urinary incontinence, frequency and urgency.