Fourteen male and female patients aged 8 to 21 (mean 12.57 years) underwent clinical and urodynamic evaluation. These patients had different lower urinary tract symptoms, and flow changes and increased perineal muscle activity during voiding were demonstrated urodynamically. The urodynamic work up consisted of flowmetry, cystomanometry, detrusor pressure-flow test, videocystourethrography and electromyography of the periurethral sphincter. The urinary symptoms were nocturnal enuresis in 6 cases (42.85%), urinary infection in 6 (42.85%), difficulty in voiding in 4 (28.57%), urgency incontinence in 4 (28.57%), voiding urgency in 2 (14.28%) and diurnal urgency and frequency in 1 case (7.18%). The following 3 voiding bladder behaviour patterns were observed; 1) involuntary micturition from bladder instability (7 cases, 50%), 2) micturition from voluntary bladder contraction (2 cases, 14.28%) and 3) absence of bladder contractile activity with voiding achieved using the abdominal muscles (5 cases, 35.71%). Decompensated voiding was observed in 21% of the overall group. Of these, 75% belonged to the group that used the abdominal muscles to void. Dilatation of the proximal or prostatic urethra was frequently accompanied by bladder instability (57%). The urodynamic data may be useful in determining the outcome of treatment.