To determine the initial response to intravesical bacillus Calmette-Guérin and the 3-year recurrence rate of high-risk non-muscle-invasive bladder cancer in patients who have asymptomatic bacteriuria. Response and recurrence rates were investigated in 505 patients with high-risk non-muscle-invasive bladder cancer after treatment with induction bacillus Calmette-Guérin (TICE strain) therapy. Initial response was determined after 3months and patients were followed every 3-6months for 3years. Before bacillus Calmette-Guérin and each follow-up cystoscopy, urine cultures were obtained, stratified as no growth, <104, >104 or>105colony-forming unit/mL. Any degree of bacteriuria on culture was classified as asymptomatic bacteriuria. Of the 505 cases, 270 (53%) had asymptomatic bacteriuria. A total of 89% of patients with asymptomatic bacteriuria showed a complete response to bacillus Calmette-Guérin versus 76% of uninfected patients (P=0.001), and 75% of bacteriuric patients survived tumor-free for 3years versus 65% of uninfected patients. Chronic bacteriuria might enhance the response of high-risk non-muscle-invasive bladder cancer to intravesical bacillus Calmette-Guérin and result in longer tumor-free survival than uninfected patients.