Pediatric liver transplantation is an effective treatment for end-stage liver disease with 1- and 5-year survivals approaching 90% and 70%, respectively. Survival is influenced by the recipient's age, weight, primary disease, vascular malformations, and nutritional status. Younger patients weighing less than 13 kg are considered to be a high-risk group. The aim of this article is to evaluate the impact of this group of patients on the overall results of our pediatric liver transplant program. From January 1986 through January 1992 we performed 76 liver transplants in 59 pediatric patients. Sixteen received a second graft and a third was required in one. Fourteen patients weighed less than 13 kg (mean, 11 kg; range, 6 to 13 kg). Their mean age was 12 months, with a range of 8 to 36 months. Indications for transplantation were: biliary atresia (9), Byler's disease (1), tyrosinemia (3), and alpha 1-antitrypsin deficiency (1). The incidence of rejection in this group (52%) was not significantly different from that in other patients (61%). Ten episodes of acute rejection required only steroids: in one monoclonal antibodies were added. Five patients had a new graft implanted, four for hepatic artery thrombosis and one for primary liver nonfunction. Nine patients are alive (64%) with the follow-up time ranging from 2 to 56 months (mean, 31). Five patients died of multiorgan failure (3), portal vein thrombosis (1), and primary liver nonfunction (1). Four-year graft and patient survival rates were 47% and 64%, respectively. Small babies are a high-risk group in a pediatric liver transplant program.(ABSTRACT TRUNCATED AT 250 WORDS)