Background: Postoperative urinary retention (POUR) is a common problem in adult neurosurgical patients. The incidence of POUR is unknown and the etiology has not been well established. POUR can lead to urogenital damage, prolonged hospital stay, higher cost, and infection. This study elucidates several risk factors that contribute to POUR in a variety of neurosurgical patients in one institution. Methods: A total of 137 neurosurgical patients were prospectively followed up for the development of POUR, which we defined as initial postvoid residual (PVR1) >250 ml 6 hours after removal of an indwelling urinary catheter (IUC). For patients with PVR >250 ml on the third check, IUCs were reinserted and kept in for 5-7 days. Results: Of the 137 patients, 68 (50%) were male, 41% (56/137) were 60 years or older, 86% (118/137) underwent spinal surgery, and 54% (74/137) had anesthesia over 200 minutes. Overall incidence of clinical POUR was 39.4% (54/137). Significantly higher rates of PVR1 >250 were noted in males, patients older than 60 years, and those who underwent spine surgery. When considering all patient characteristics (except selective alpha blockers), only gender, surgery time, and surgery type remained significant. In addition, PVR1 >250 was positively associated with longer length of stay. Of all patients, 24 (18%) had IUCs reinserted postoperatively or should have had one (5 refused and 2 had a third PVR). The association of IUC reinsertion with male gender was significant. Conclusion: Male gender, time of anesthesia >200 minutes, older age, and spinal surgery are the most significant risk factors associated with POUR in neurosurgical patients.