Purpose We evaluated the effectiveness of bladder neck injection as a supplementary treatment for persistent low pressure incontinence after unsatisfactory fascial sling procedures in patients with neurogenic lower urinary tract dysfunction. Materials and Methods A total of 89 patients with neurogenic lower urinary tract dysfunction underwent fascial sling procedures between 1992 and 2005. Because of unsatisfactory results, 27 patients received endoscopic injection of a bulking agent. All patients included in the study underwent urodynamic examination after the sling procedure, which revealed persistent low pressure transurethral leakage of urine. We retrospectively analyzed the endoscopic approach used to administer the bladder neck injection, method of postoperative catheterization and number of injections given. Efficacy of bladder neck injection was graded by the patient and the urologist. Results After a median followup of 8 years (range 2.5 to 14) only 2 patients (7%) were continent after having received a single injection of bulking agent. A total of 12 patients (44%) were given a second injection and 8 (30%) were given a third injection but these subsequent injections did not result in continence. Of the patients 16 (59%) eventually underwent bladder neck surgery, 2 (7%) were dry and 8 (30%) accepted the inconvenience. Two patients underwent ileocystoplasty and 1 patient underwent botulinum A toxin (Botox®) injection due to decreased bladder capacity and poor bladder compliance. Neither the endoscopic approach nor the method of postoperative catheterization affected the success rate. Conclusions Bladder neck injection after failure of primary sling procedures has limited value in patients with neurogenic lower urinary tract dysfunction. Repeat bladder neck injection yields no additional benefits.