 In this 2-year, multisite, randomized, placebo-controlled trial involving 607 children with vesicoureteral reflux that was diagnosed after a first or second febrile or symptomatic urinary tract infecton, we evaluated the efficacy of Trimethoprim-Sulfamethoxazole TMP-SMZ prophylaxis in preventing recurrences primary outcome. Secondary outcomes were renal scarring, treatment failure a composite of recurrences and scarring, and antimicrobial resistance. 