This study examined the difference in postoperative bacteriuria in total joint arthroplasty after use of either an indwelling catheter or intermittent catheterization. Previous studies showed a preference for an indwelling catheter over intermittent catheterization to resolve postoperative urinary retention in total joint arthroplasty, but these studies generally used 48 hours of antibiotic prophylaxis. Increasing awareness of costs and bacterial resistance to antibiotics have prompted many centers to reduce prophylaxis to only 1 preoperative dose A prospective, randomized, controlled trial was conducted in primary total hip and primary total knee arthroplasty patients. One dose of cefazolin, 1 g, was administered intravenously immediately preoperatively. Five of 13 (38%) men in the indwelling catheter group and 0 of 14 (0%) men in the intermittent catheterization group developed postoperative bacteriuria (P =.016), and 6 of 33 (18%) women in the indwelling catheter group and 3 of 39 (8%) women in the intermittent catheterization group developed postoperative bacteriuria (not significant). A total of 11 (24%) patients in the indwelling catheter group (n = 46) and 3 (6%) patients in the intermittent catheterization group (n = 53) developed postoperative bacteriuria (P =.018). In this setting with 1-dose antibiotic prophylaxis, intermittent catheterization resulted in a lower incidence of postoperative bacteriuria compared with an indwelling catheter. For men, this difference is significant.