Orthotopic liver transplantation (OLT) is nowadays accepted as the best therapy for end-stage liver disease. The difficulties involved are even greater in children than in adults, and it is debatable whether exclusively pediatric programs are warranted. The aim of this paper is to analyze our experience at the Children's Hospital "La Paz", with the first consecutive 100 OLT in children, 61% of whom weighed less than 20 kg. Since 1986, 220 pediatric patients were evaluated as candidates, 100 OLT were performed in 78 patients and 13 died on the waiting list, currently maintained below 15 cases. Indications were: cholestasis (45), metabolic disease (18), fulminant hepatic failure (3), primary liver tumors (2) and cirrhosis (10). Mean age was 66 months (range = 7 to 216) with a mean weight of 21 kg (range = 6 to 60), twenty patients weighed less than 13 kilograms. OLT was performed by standard technique. Reduced or segmental grafts were necessary in 8 instances. Twenty-two patients were retransplanted and 2 received three grafts. Indications for retransplantation were: hepatic artery thrombosis (8), primary nonfunction (4), chronic rejection (7), portal thrombosis (2) and Budd-Chiari recurrence (1). Acute rejection was observed in 52 patients, and eight cases developed a chronic rejection. These episodes were treated with "bolus" of steroids, monoclonal antibodies (OKT-3) and FK-506. Surgical complications included: hepatic artery thrombosis 12%, portal vein thrombosis 3% and biliary fistula or stenosis 13%. The incidence of primary non-function was 7%. Actuarial survival rate at 5 years was 75%.(ABSTRACT TRUNCATED AT 250 WORDS)