Objective: To estimate whether nitrofurantoin prophylaxis decreases the incidence of culture-documented urinary tract infection for women with catheter-managed urinary retention after pelvic reconstructive surgery. Methods: This double-blind, placebo-controlled, randomized trial was conducted at five academic institutions. Women with urinary retention after surgery for prolapse or incontinence were randomized to oral nitrofurantoin 100 mg daily during indwelling or clean intermittent self-catheterization. The primary outcome was the incidence of symptomatic urinary tract infection within 6 weeks of surgery, confirmed by culture demonstrating more than 1,000 colony forming units per milliliter of uropathogenic bacteria. Secondary outcomes were adverse symptoms possibly attributable to nitrofurantoin and bacterial resistance to nitrofurantoin. A sample size of 154 would detect a decrease in urinary tract infection incidence from 33% to 13%, with 80% power, two-sided alpha of 0.05, and allow 10% dropout. Results: Of 154 participants randomized from September 2016 to May 2018, 151 were eligible for analysis: 75 received nitrofurantoin, and 76 received placebo. Demographics were similar between groups. The indication for surgery was prolapse (46%), incontinence (20%), or a combination (34%). Participants were discharged with an indwelling catheter (58%) or performing self-catheterization (42%). Median duration of catheter use was 4 days (interquartile range 3-7). Thirteen women in the nitrofurantoin group and 13 women in the placebo group experienced urinary tract infection (17.3% vs 17.1%, P=.97, relative risk [RR] [95% CI] 1.01 [0.50-2.04]). Adverse symptoms possibly attributable to nitrofurantoin were common in both groups (68% vs 61%, P=.34, RR [95% CI] 1.12 [0.88-1.43]). Resistance to nitrofurantoin was identified in seven urine cultures, four among nitrofurantoin and three among placebo recipients. In total, 52 urine cultures were obtained to evaluate symptoms of urinary tract infection, and only 27 of 52 grew at least 1,000 cfu/mL of uropathogenic bacteria. Conclusion: Daily nitrofurantoin did not reduce the incidence of culture-proven urinary tract infection among women with catheter-managed urinary retention after pelvic reconstructive surgery. Culture confirmed urinary tract infection in only half of symptomatic episodes.