A prospective analysis of 166 women with genuine stress incontinence was performed comparing Valsalva leak-point pressure (VLPP) and maximum urethral closure pressure (MUCP) with age, previous urogynecologic surgery and/or hysterectomy, poor urethral mobility, weight, menopause and vaginal deliveries, to find correlations with intrinsic sphincter deficiency (ISD). Cut-off value for VLPP were 60 cmH2O and for MUCP 30 cmH2O. MUCP < or = 30 cmH2O identifies a group of patients with more severe incontinence, a shorter urethral functional length (UFL) (P = 0.02), more previous urogynecologic operations and the menopause (P = 0.004 and P = 0.000), and older age (P = 0.000). VLPP < or = 60 cmH2O identifies a group of patients with more severe incontinence, a shorter UFL (P = 0.005), more previous urogynecologic surgery (P=0.006) and poorer urethral mobility (P = 0.004). As these two tests measure different components of urethral functions we can hypothesize that they detect different pathogenic processes contributing to ISD. When one or both tests is abnormal incontinence is more severe and the incidence of poor prognostic factors is increased.