Postoperative urinary retention (PUR) rates vary greatly depending on the population studied. PUR leads to urinary tract instrumentation, which causes increased hospital costs and morbidity. We sought to determine our PUR rate and the risk factors that associated with it. One hundred seventy-six adult surgical inpatients were included in the study. Excluded were those receiving intraoperative catheterization, epidural anesthesia, and urologic procedures. The study population included 42 per cent spinal, 24 per cent laparoscopic abdominal, 20 per cent neck surgeries excluding the spine, and 14 per cent miscellaneous surgeries. Patient bladder volumes were determined using ultrasound scanning at three different intervals: a postvoid residual just before transfer to the operating suite, immediately on arrival in the recovery unit, and then immediately before transfer to the ward. Our overall rate of PUR was 5.7 per cent (10 of 176), defined as the need for catheterization during the postoperative hospitalization. Associated with PUR were advanced age (P = 0.0292) and postoperative bladder volume (P = 0.0246). Preoperative bladder volume, intraoperative fluid, and operative time did not reach statistical significance as being predictive of urinary retention. Our data suggest that PUR is associated with increased bladder volumes on arrival to the recovery room. A prospective study to determine whether identification of patients at risk will lead to decreased incidence of urinary tract infection is warranted.