In traumatic rupture, it is often not possible to repair the spleen. Splenectomy results in increased susceptibility to sepsis with a high mortality rate. Autotransplantation of splenic tissue has been suggested, but its functional value is still in doubt, particularly the ability of autotransplanted spleen to resist intravenous bacterial challenge. The ability to sequestrate denatured 99roTe (technetium-99m) RBC (red blood cells) and to resist intravenous pneumococci was studied in sham-operated (control) rats, splenectomized rats, and splenectomized rats with autotransplanted spleen. Histopathologic tests were also performed. There was a gradual increase in the splenic sequestration of the denatured 99mTc RBC with a spleen-to-blood ratio of 0.19 to 1.5 at 2 and 30 weeks after the splenic reimplantation. Prior to 18 weeks after the splenic autotransplantation, no rat survived the intravenous pneumococcal challenge, but at 28-30 weeks, 80% of the rats survived the challenge indicating an increased splenic activity at this time. There was also a corresponding increase in splenic tissue weight from 241 mg at the time of autotransplantation to 417 mg beginning at the 24th week after the reimplantation. Four to 5 weeks after the transplantation, the spleens had a fairly normal histological architecture. The present study, therefore, indicates that autotransplanted splenic tissue is capable of restoring the ability to resist intravenously injected pneumococcai challenge, to sequestrate denatured 99mTC RBC, and to regenerate normal splenic tissue within 24-30 weeks after the reimplantation.Traumatic rupture of the spleen is a common injury especially in victims of road traffic accidents. Often the injured spleen cannot be repaired and splenec-