We evaluated the efficacy of tolterodine extended release (ER) for patients' most bothersome overactive bladder (OAB) symptom in a primary care setting. Patients with OAB symptoms for >or=3 months received tolterodine ER (4 mg q.d.) for 12 weeks. Among incontinent patients (n = 772), the most bothersome OAB symptoms were daytime frequency (28%), urgency urinary incontinence (UUI; 27%), nocturnal frequency (26%) and urgency (19%); among continent patients (n = 91), they were daytime frequency (47%), nocturnal frequency (42%) and urgency (10%). Sixty-nine per cent of patients had one or more comorbid conditions. By week 12, there were significant reductions in patients' most bothersome symptom: -80% for UUI, -78% for urgency episodes, -40% for nocturnal frequency and -30% for daytime frequency (p < 0.0001). The most common adverse events were dry mouth (10%) and constipation (4%). In primary care practice, bothersome OAB symptoms can be effectively and safely treated with tolterodine ER, even in patients with comorbid conditions.