Background. Pediatric liver transplant recipients have traditionally been grouped according to age. Age-based classification schemes are useful in identifying clinical problems in selected age groups and also for developing solutions to these problems. Although infants in the first 3 months of Life have not traditionally been considered a distinct age group, several features of these infants may distinguish them from other pediatric liver transplant recipients. Methods. The experience with liver transplantation in infants during the first 3 months of life in three large pediatric Liver transplant programs (University of Chicago, Stanford University, and UCLA) was analyzed in order to characterize this group. Results. A total of 23 liver transplants were performed at these three centers in children younger than 3 months of age. This group of patients comprised approximately 37% of the U.S. experience between 1988 and 1994 according to United Network for Organ Sharing statistics. Age distribution at the time of transplantation included the following: <1 month, 28%; 1-2 months, 35%; and 23 months, 36%. Median age at the time of transplantation was 37 days (range, 7-90 days), and mean age was 57+/-30 days. Mean weight at the time of transplantation was 3.8+/-1.0 kg. Etiology of liver disease included idiopathic hepatitis, 52%; iron storage disease, 17%; and other causes, 31%. Types of liver allografts used included cadaveric, 85% (reduced size, 60%, and full-size, 25%); living donor, 15%; ABO-identical, 65%; and ABO-compatible, 35%. Actuarial patient and graft survival rates were 60% and 60% at 1 year and 60% and 42% at 2 years, respectively. Median follow-up was 1.5 years. Rejection occurred in 42% of patients, with a median time to first rejection of 13 days. Of these patients, 28% required steroids only and 14% required OKT3. Three patients (14%) were retransplanted at a median time to retransplantation of 1.6 years. Vascular thrombosis occurred in three patients (14%). Conclusions. Liver transplantation performed in infants younger than 3 months of age (1) provides acceptable short- and long-term patient and graft survival, (2) is associated with significant rates of rejection, and (3) is not associated with excessive rates of vascular thrombosis. The etiology of end-stage liver disease occurring in the first 3 months of life is distinct from that in other pediatric liver transplant recipient age groups. These infants should be referred promptly for liver transplantation as reasonable survival can be expected.