The function of replanted splenic fragments was studied by comparing three groups of five dogs each, one group with intact spleens; one, post-splenectomy; and one with splenic replantation. Fifteen fragments were implanted into the omentum. Howell-Jolly bodies appeared after splenectomy but cleared in the replanted group after several months. I125-tagged attenuated pneumococcal clearance studies showed a significant difference between control and replanted group compared with the splenectomized group. The increase of pneumococcal antibody titers after vaccination differed significantly between the splenectomized and the replanted group. All replanted fragments were viable and showed growth over a 2-year period. These studies demonstrate that omental replantation of the canine spleen leads to the maintenance of certain functional splenic parameters comparable to the normal spleen which are significantly different from the splenectomized animal.