The use of urodynamic testing must be selective and based on the particular patient's complaints. In today's cost-conscious health care environment, a diagnosis based on one or two tests is preferable to exposing each patient to the full battery of available tests. For most patients, a cystometrogram and voiding cystourethrogram can confirm a variety of clinical suspicions. A cystometrogram best indicates how the bladder is behaving during filling. The voiding cystourethrogram allows the physician to observe the bladder and urethra during voiding and offers an excellent view of the anatomic relations of the urologic organs in the pelvis. The other important benefit of urodynamics is the objective data made available in hardcopy as a baseline study to be utilized for comparison in the future. The normal sequence of testing is a noninvasive uroflow study to determine the baseline flow rate. The postvoiding residual volume of urine is then determined. A cystometrogram and electromyography can then be done, the latter if there is a suggestion of neurologic disease or if otherwise indicated to determine bladder behavior on filling. Variations that are helpful when a patient fails to have a bladder contraction include having the patient in an upright or seated position during the test. A bethanechol supersensitivity test may be indicated as well. The urethral pressure profile may be done as the catheter is withdrawn and the bladder is already filled. The filled invasive flow rate can then be compared with the free flow rate. Sometimes, one of these rates is abnormal, and there is a question about whether the abnormality is real. The residual urine volume can be determined by subtracting the volume the patient voids from the filling volume. In the end, the key to urodynamic evaluation is the interpretation of the test, which should be made only by the individual actually performing the test. It truly is necessary for the physician to be there in person. Selective use of urodynamics can target an appropriate treatment for most patients. The female patient who complains of incontinence in whom the history suggests detrusor instability may benefit from a trial of cholinolytic therapy if no anatomic defect is present. In this type of patient, a surgical procedure may not be of benefit, whereas the cholinolytic therapy probably will work. This is a good reason for always choosing the appropriate urodynamic tests for evaluating and planning treatment for patients with urinary incontinence.