Tolterodine was developed as an antimuscarinic agent specifically for the treatment of overactive bladder. Initial in vivo studies demonstrated a functional selectivity for the muscarinic receptors in the urinary bladder over the salivary glands, and subsequent clinical trials showed an overall superior tolerability profile compared with other drugs in the same class (ie, oxybutynin). With immediate- and extended-release formulations and sustained clinical efficacy during long-term treatment, tolterodine gas become an important treatment option for the symptoms of overactive bladder.