Stress urinary incontinence was evaluated urodynamically in 86 women in private urologic practice. While 31 patients had failed prior surgical repairs and 58 patients (67.4 per cent) reported irritative symptoms of frequency, nocturia, urgency and urge incontinence unstable bladders were found in only 5 women (5.8 per cent) over-all, in 6.5 per cent of those patients failing a previous operation and in 8.6 per cent of those patients with irritative symptoms. Urethral pressure profiles were decreased mildly in patients with, compared to those without, stress urinary incontinence but considerable overlap existed and no improvement was seen in 20 patients cured with an operation. Excretory urography, post-voiding residual urine volumes and sphincter electromyography usually were normal. Women with stress urinary incontinence consistently showed poor transmission of cough to the urethra so that the intravesical pressure exceeded the intraurethral pressure.