Management strategy for upper urinary tract calculi in small children is still a matter controversial. We report successful management of ureteral stone with transurethral ureterolithotripsy (TUL) in 2 boys weighing around 10 kg. Case 1: A 2-year-old boy (78 cm in height, 9.6 kg in weight), who received hydrocortisone and fludrocortisone for the treatment of 21-hydroxylase deficiency, was referred to our hospital with a right 9-mm lower ureteral stone. For TUL, a 7.5 Fr rigid cystoscope was introduced into the ureter directly after dilation of the ureteral orifice. By using Holmium:YAG laser for lithotripsy, complete stone evacuation was achieved. Stone analysis showed the composition of calcium phosphate and calcium oxalate. Case 2: A 1-year-old boy (80 cm in height, 10.5 kg in weight) with neurofibromatosis type 1 was referred to our hospital with a left 7.5-mm ureteral stone at the ureteropelvic junction. TUL was performed using a 4.5 F rigid ureteroscope and Holmium:YAG laser. No residual stone was identified. Stone analysis showed the composition of calcium oxalate. TUL is a safe and feasible option for small children, even in boys weighing approximately 10 kg.