OBJECTIVE: To evaluate the efficacy and safety of low-dose (2 mg) tolterodine extended release (ER) with an α-blocker compared with standard-dose (4 mg) tolterodine ER with an α-blocker for the treatment of men with residual storage symptoms after α-blocker monotherapy. PATIENTS AND METHODS: The study was a 12-week, single-blind, randomized, parallel-group, non-inferiority trial that included men with residual storage symptoms despite receiving at least 4 weeks of α-blocker treatment. Inclusion criteria were total International Prostate Symptom Score (IPSS) ≥12, IPSS quality-of-life item score ≥3, and ≥8 micturitions and ≥2 urgency episodes per 24 h. The primary outcome was change in the total IPSS score from baseline. Bladder diary variables, patient-reported outcomes and safety were also assessed. RESULTS: Patients were randomly assigned to addition of either 2 mg tolterodine ER (n = 47) or 4 mg tolterodine ER (n = 48) to α-blocker therapy for 12 weeks. Patients in both treatment groups had a significant improvement in total IPSS score (−5.5 and −6.3, respectively), micturition per 24 h (−1.3 and −1.7, respectively) and nocturia per night (−0.4 and −0.4, respectively). Changes in IPSS, bladder diary variables, and patient-reported outcomes were not significantly different between the treatment groups. All interventions were well tolerated by patients. CONCLUSIONS: These results suggest that 12 weeks of low-dose tolterodine ER add-on therapy is similar to standard-dose tolterodine ER add-on therapy in terms of efficacy and safety for patients experiencing residual storage symptoms after receiving α-blocker monotherapy.