Urodynamic examination yields invaluable information about lower urinary tract function in infants and children in the following clinical situations: Daytime urinary incontinence, suspected infravesical obstruction, overt or suspected neurogenic bladder dysfunction, vesico-ureteral reflux with upper tract dilatation and chronic or recurrent bacteriuria. A normal development of lower urinary tract function during the first 5 years of life means that detrusor contractility will be successively more inhibited; furthermore, the child will become aware of bladder filling and will be able to postpone or initiate micturition. A disturbed or delayed development may well be the most important cause of dysfunctional states in the lower urinary tract later in life. Most urodynamic variables are age-dependent. Normal bladder capacity can be fairly well assessed by: Bladder capacity in ml = 30 + (age in years x 30). Normal maximum urinary flow during micturition (in ml/s) should approximately equal the square root of voided volume (in ml). The normal range (+/- 2SD) is given by the value thus obtained +/- 7 ml/s. Intravesical pressure is lower in girls than in boys, and lower in infants than in older children, but otherwise it does not vary with age. A tense and apprehensive child will not produce reliable urodynamic data. This is, no doubt, the most important source of error when examining children. It is strongly emphasized, therefore, that the examination has to be performed in a kind, understanding and relaxed atmosphere.