OBJECTIVE Detrusor underactivity (DU) is a common urologic problem and usually presents with urine retention or large postvoid residual (PVR). Medical treatment of DU does not always achieve satisfactory results. We report the surgical outcomes of transurethral incision of the bladder neck (TUI-BN) in women with DU and urine retention. METHODS A total 31 woman with DU in whom medical treatment failed underwent TUI-BN and were retrospectively studied. Surgical outcome was determined by postoperative urodynamic studies and clinical presentation. Patients with postoperative voiding efficiency of >67% had excellent outcomes, those with 33-66% had moderate results, and those with <33% had poor surgical outcomes. RESULTS PVR, voiding efficiency, and maximum urinary flow rate (Qmax) significantly improved after TUI-BN. PVR decreased by 56.3% overall. Intermittent catheterization was needed in 27 patients before surgery and in only seven after TUI-BN. There were 14 (45.2%), 11 (35.5%), and six (19.3%) patients with excellent, moderate, and poor surgical outcomes, respectively. Baseline urodynamic parameters, age, and etiologies did not impact surgical outcome. Three patients developed transient urinary incontinence, and one developed vesicovaginal fistula after TUI-BN. CONCLUSIONS TUI-BN is an effective procedure to improve PVR, Qmax, and voiding efficiency in women with DU and urine retention. The procedure is safe and effective, even in patients with medical treatment failure, those with large PVR at baseline, and those with different etiologies.