Two infants with short-bowel syndrome and liver failure associated with obligatory parenteral nutrition received a composite allograft that consisted of en bloc liver, stomach, duodenum, pancreas, jejunum, and ileum. Solutions to the fatal complications in the first case resulted in a functioning composite splanchnic system in the second case. Despite a number of early complications, the small intestine and liver developed near-normal function until a monoclonal, malignant, B-cell lymphoproliferative disorder appeared. The analysis of these two cases supports three summary observations: the operative procedure can be safely performed in a metabolically compromised infant; intestinal allograft rejection, in this model, is controllable with existing immunosuppressive drugs; and this procedure appears to be associated with a uniquely high incidence of lymphoma. Since transplantation is a feasible solution to this devastating infantile disease, further development of this therapy must incorporate means of preventing lymphoma.