INTRODUCTION AND HYPOTHESIS: This study's aims were to detect and quantify bacterial DNA in the urine of randomized trial participants about to undergo treatment for urinary urgency incontinence (UUI) without clinical evidence of urinary tract infection (UTI) and to determine if the presence of bacterial DNA in baseline urine relates to either baseline urinary symptoms or UTI risk after urinary tract instrumentation. METHODS: Women without clinical evidence of baseline UTI were randomized to cystoscopic onabotulinum toxin A injection and oral placebo medication versus cystoscopic placebo injection and active oral medication. Bacterial DNA in participants' catheterized urine was measured by quantitative polymerase chain reaction (qPCR). RESULTS: Bacterial DNA was detected in the urine of 38.7 % of participants (60 out of 155). In these 60 qPCR-positive participants, baseline daily UUI episodes were greater than in the 95 qPCR-negative participants (5.71 [±2.60] vs 4.72 [±2.86], p = 0.004). Neither symptom severity by questionnaire nor treatment outcome was associated with qPCR status or with qPCR level in qPCR-positive subjects. In contrast, the presence of urinary bacterial DNA was associated with UTI risk: only 10 % of the qPCR-positive women developed a UTI post-treatment, while 24 % of the qPCR-negative women did so. The median qPCR level for qPCR-positive samples did not differ significantly by UTI status (UTI 2.58 × 10(5) vs no UTI 1.35 × 10(5) copies/mL, p = 0.6). CONCLUSIONS: These results may indicate a urinary bacterial contribution to both baseline UUI and the risk of post-treatment UTI.