The histology of regenerated ectopically implanted spleen (splenotic tissue) from splenectomized rats was compared with that of normal rat spleen. Computer-assisted morphometric analysis revealed significant decreases in both the number and area of splenic nodules in splenotic tissue when compared with normal spleen. It is suggested that the reduction in the amount of white pulp present could explain at least in part the reduced ability of splenotic tissue to deal with infection.