Biopsy is the best way to diagnose allograft rejection, the most common complication following liver transplantation. The authors reviewed 99 consecutive ultrasound-guided cutting needle biopsies in 19 infants and children. Conscious sedation was used with 95 biopsies. General anesthesia was used with four biopsies, all in patients undergoing percutaneous biliary procedures at the same time. Ninety-eight biopsies were diagnostic. Only one major complication occurred: biloma. Ultrasoundguided cutting needle biopsy of pediatric liver transplant patients can be performed safely and efficaciously.