To date, rigid operative ureterorenoscopy with ultrasound lithotripsy for the treatment of ureteral calculi has been performed only in adults or older children. The size of the instrument with the working channel for the ultrasound probe has been considered unsuitable for delicate anatomical structures, such as those of children younger than 4 years. We performed 8 ureterorenoscopic examinations in 7 patients (3 boys) 3 to 8 years old and have demonstrated that the 11.5F ureteroscope can be inserted without difficulty into the ureteral meatus of a 3-year-old boy. Introduction of the instrument is facilitated by the use of the Perez-Castro irrigation pump. This procedure does not lead to any urethral or ureteral damage, nor is vesicoureteral reflux shown on a postoperative cystogram. This technique allows extracorporeal shock wave lithotripsy to be extended also to small children, offering the possibility of easy and successful management of any residual steinstrasse.