AIMS: To confirm the idea that women with stress incontinence can have elevated postvoid residual urine (PVR) and to examine the correlation between PVR obtained with catheterization versus that with BladderScan (BS). MATERIALS AND METHODS: This is a prospective study involving 902 women referred to our urogynecology clinics because of symptoms of lower urinary tract dysfunction. Women were selected if they met all of the following conditions: (1) A main complaint of stress urinary incontinence; (2) A diagnosis of urodynamic stress incontinence; and (3) No previous pelvic surgery, advanced pelvic prolapse or neurological deficit. One hundred and seven women met all criteria and formed the basis for this study. All women in the study group underwent three-part urodynamic testing including uroflowmetry, filling (provocative) and voiding cystometry. After uroflowmetry they were scanned by a BS, and then catheterized for PVR volume before the procedure of cystometry. RESULTS: The mean PVR volume was 62.8 ml by BS and 38.5 ml by catheterization. 35.5% women had PVR urine higher than 50 ml and 15.9% had PVR urine greater than 100 ml. The PVR volume obtained by BS correlated significantly with catheterized volume (r = 0.625, P = 0.001) and offered a sensitivity of 64.7% and a specificity of 94.3% in detecting PVR greater than 100. The mean maximum flow rate was 22.1 ml/sec and mean detrusor contraction pressure during voiding was 21 cm H(2)O. CONCLUSIONS: Women in our study had low maximum flow rate (22.1 ml/sec), elevated PVR (38.5 ml) and high detrusor contraction pressure during voiding (21 cm H(2)O) indicating that women with stress incontinence have some degree of voiding dysfunction. The bladder behavior in women with stress incontinence may be more complex than we had previously considered and special care should be taken if a woman with elevated PVR is scheduled for anti-incontinence surgery. BS appears to be reasonably sensitive and specific for the detection of elevated PVR and is reliable in clinical use.