OBJECTIVE A prospective study was performed to determine the incidence of significant bacteriuria and to identify the risk factors for bacteriuria after urodynamic studies (UDSs) in women with urodynamic stress urinary incontinence (SUI). METHODS A total of 225 women with urodynamic SUI were evaluated. All women were negative on double-screened urine cultures, in clean-catch midstream urine (MSU) specimens, before UDS. Another urine specimen was obtained for urinalysis and culture at 3-7 days after UDS. Urinary culture with 10(5) CFU/ml or more was regarded as significant bacteriuria. To identify the risk factors for significant bacteriuria, the clinical characteristics of all patients including age, BMI, parity, medical and operation history, degree of pelvic organ prolapse, results of urinalysis, and UDS were evaluated. RESULTS The prevalence of significant bacteriuria was 6.2%. The most common identified microorganism was Escherichia coli (57.1%). Univariate analysis demonstrated that a history of recurrent urinary tract infection (UTI; P = 0.002) and urological surgery or procedure (P = 0.02) were significant predictors of significant bacteriuria. On multiple logistic regression analysis the past history of recurrent UTI was the only significant independent risk factor (OR = 28.5, 95% CI = 4.309-188.488, P = 0.009). CONCLUSIONS This study suggests that for most women with SUI it may be unnecessary to use preventive prophylactic antibiotics in UDS. However, our results suggest that in patients with a previous history of recurrent UTI or urologic surgery the risk for significant bacteriuria is increased and use of prophylactic antibiotics should be considered.