Introduction: The emergence of urinary retention (UR), specifically acute urinary retention (AUR), has been a concern when treating men with lower urinary tract symptoms (LUTS) with antimuscarinic drugs. Materials and methods: In NEPTUNE (12-week, double-blind), men (≥45 years) with LUTS were randomized to receive tamsulosin oral-controlled absorption system (TOCAS) 0.4 mg, fixed-dose combination (FDC) of solifenacin (Soli) 6 mg + TOCAS 0.4 mg, FDC Soli 9 mg + TOCAS 0.4 mg, or placebo. In NEPTUNE II (40-week, open-label extension of NEPTUNE), continuing patients received 4-week FDC Soli 6 mg + TOCAS, then FDC Soli 6 mg or 9 mg + TOCAS for the remainder of the study, switchable every 3 months. Results: Across both studies, 1208 men received ≥1 dose of FDC Soli 6 mg or 9 mg + TOCAS for up to 52 weeks; 1199 men completed NEPTUNE and 1066 received ≥1 dose in NEPTUNE II. In total, 13 men (1.1%; 95% CI, 0.6%-1.8%) reported a UR event while receiving FDC, eight of which were AUR (0.7%; 95% CI, 0.3%-1.3%, incidence 7/1000 man-years). Six men reported UR events while taking Soli 6 mg + TOCAS (three AUR), and seven men reported a UR event while taking Soli 9 mg + TOCAS (five AUR). One man developed AUR while taking TOCAS alone and four reported UR (three AUR) during placebo run-in. Most AUR/ UR events occurred within 4 months of treatment initiation. Conclusions: FDC Soli and TOCAS was associated with a low rate of UR and AUR in men with LUTS.