Urodynamics is becoming established as a useful means of evaluating the lower urinary tract to differentiate among the varieties of voiding dysfunction and investigate neuropathic involvement of the urinary bladder and the sphincteric mechanism. Its value is now recognized not only for urodynamic problems but also for pediatric and geriatric voiding disorders. From the time when a urodynamic study denoted the simple observation of the urinary stream, the field has progressed with the development of sophisticated instruments to obtain complex recordings of various parameters in the lower urinary tract, the pelvic floor musculature, and intra-abdominal pressure. Urinary flowmetry, urethral profilometry, cystometric studies, assessment of pure detrusor activity, response to dynamic changes in intra-abdominal pressure and patient position, as well as in the state of the bladder filling, are all becoming an integral part of a complete study of the lower urinary tract. Mixing urodynamic study with fluoroscopic imaging links anatomical changes to functional alterations; when this is coupled with testing with various pharmacologic agents, the investigation becomes an indispensable means to evaluate the urologic patient with a voiding disturbance.