The accuracy of the urethral pressure profile as a measure of sphincteric competence was examined in female subjects. Most profile measurements selected proved to be significantly different in patients with stress incontinence from those in controls. However, the measurement that seemed to have the highest potential for diagnostic accuracy was the maximum closure pressure in the continence zone, recorded with the bladder full and the patient standing. The concept of the continence zone and incorporating the effect of standing were believed to be the main reasons for this high accuracy. The second best measurement was the maximum closure pressure with the bladder full and the patient surpine. To lessen the chances of a diagnostic error it was recommended that both of these measurements should be obtained. The physiological implications of these findings and the clinical role of the urethral pressure profile examination in the assessment of female patients with urinary incontinence are discussed.