The lower urinary tract is a complicated structure and there has been some controversy regarding the biomechanics and dynamics of bladder and sphincter function. Investigation of the function and morphological anomalies is very important. Videourodynamics (VUD) combined with conventional voiding cystourethrography (VCUG) seems to be the most appropriate method. Over a 12-year study period (January 1990 to December 2001), 422 children (aged 5 days to 20 years) prospectively underwent VUD to further define their urinary tract abnormalities. In all children the history was recorded, clinical examination, urinalysis, culture, and ultrasonography performed, and serum creatinine determined before VUD. The selection criteria included a history of recurrent urinary tract infections (UTI) in 310 patients (74%), urinary tract dilatation without UTI in 31 patients (7%), suspected neurogenic bladder dysfunction in 42 patients (10%), and voiding difficulties in 39 patients (9%). VUD consists of cystometry (CM), which is the measurement of detrusor pressure during controlled bladder filling and subsequent voiding, and was combined with VCUG using X-ray contrast material. CM is used to assess detrusor activity, sensation, capacity, and compliance. CM measurements were recorded on a computer and vesicoureteric reflux (VUR) was documented at the same time with plain films and later in a PACS system. The VUD diagnosis was of normal bladder function in 46 patients (9%), VUR in 212 (43%), unstable bladder dysfunction in 152 (31%), neurogenic bladder dysfunction in 35 (7%), urine outflow obstruction in 15 (3%), wide bladder neck in 22 (4%), and vaginal reflux in 9 (2%). Neurogenic bladder dysfunction was excluded in 7 patients (1%). VUD is useful for the investigation of the lower urinary tract function together with X-ray morphology. The advantage of these studies is that they combine the objectivity of urodynamics with the visual radiographic image, leading to lower radiation doses and a more logical interpretation of the results.