Background Intrinsic sphincter deficiency (ISD) is associated with an inability to maintain mucosal coaptation either at rest or in the presence of stress resulting from damage to muscles or nerves that maintain tonus. The purpose of our trial was to determine the role of urodynamic measurements of flow such as maximum flow rate, flow time, and acceleration speed of flow to assess the urethral resistance on prediction of stress incontinence and ISD. Materials and Methods Our study was based on a retrospective analysis of urodynamic records of female patients performed for urinary incontinence. Mean flow rate, maximum flow rate, detrusor pressure at maximum flow, vesical pressure at maximum flow, maximum detrusor pressure, and flow rate at maximum detrusor pressure measurements were extracted from the voiding phase of urodynamic charts. The slope of the maximum flow was used to calculate acceleration of flow (Qacc). The urodynamic records of 142 women were reviewed and Qacc was measured. Results The mean age of the ISD group was 53.3 +/- 12.5 (24-78) and of the non-ISD group 53.7 +/- 12.5 (35-74). The mean Qacc (30.3 +/- 16.1 degrees [mL/s(2)]) in the ISD group was significantly higher than in the non-ISD group (21.6 +/- 9.6 degrees [mL/s(2)]). Urodynamic bladder capacity of the non-ISD group (432.3 +/- 90.4 mL) was higher than the ISD group (389.2 +/- 109) (P = .01). Conclusion The Valsalva leak point pressure and maximum urethral closure pressure measurements in assessing urethral function are not useful for predicting incontinence surgery failure. We demonstrated that Qacc is higher in ISD stress incontinent women than stress incontinent women. Qacc may demonstrate urethral resistance and tonus in a more reliable manner.