Tolterodine has emerged as a new anticholinergic drug to treat detrusor instability in recent years. This substance and its major metabolite DD01 exhibit a favourable effect-to-side-effect ratio for the bladder. Several clinical studies demonstrated the drug's efficacy in reducing the symptoms of an overactive bladder (urgency, urge incontinence and high micturition frequency) and in increasing functional bladder volume. With a clinical effectiveness comparable to oxybutynin, the side effect-profile measures up favourably to oxybutynin. Consequently, though some limitations need to be addressed, tolterodine can be regarded as the drug of first choice to treat overactive bladders in a variety of patient groups: the young (and otherwise healthy), the elderly, as well as in patients with renal and hepatic insufficiency. A new extended release formula of tolterodine has been launched that may improve patients' compliance.