Purpose : The conventional Whitaker test assesses the renal pelvic pressure response to a constant infusion rate of 10 mL/min in adult and 5 mL/min in children. We evaluated whether the infusion rate,5 mL/min is appropriate during Whitaker test in children. Materials and Methods : The study included 3 children with unilateral hydronephrosis, whose diuretic renography results were equivocal to define the presence of urinary obstruction. The kidneys were perfused at increasing flow rates from lmL/min. Results : There were intrapelvic pressure increases $26;cmH_2O$ at 3 mL/min, $50;cmH_2O$ at 2 mL/min and $80;cmH_2O$ at 3 mL/min infusion rate, respectively. There was no need to increase the infusion rate over 4 mL/min to get a positive Whitaker test. Conclusion : Our experience with Whitaker test at variable low flow rates (1-5 mL/min) confirmed its usefulness in differentiating obstructive from nonobstructive uropathy. We recommend the increasing infusion rate from 1 mL/min during Whitaker test in children.