This study is concerned with the choice between conservative and surgical treatments for equivocal unilateral Ureteropelvic junction obstruction in infants. Twenty six cases had been included. Progress of the Anteroposterior diameter of renal pelvis and split renal function of the affected kidney, had been recorded. And it was concluded that increase in AP diameter more than 3 cm, may be a strong guideline for immediate surgery to avoid expected renal deterioration, And if Ap diameter at presentation was less than 3 cm , so it is better give chance for conservative mangment.