Following splenectomy, infant rats are at risk when challenged with pneumococcus. Mortality was 85% in splenectomized rats and 6.6% in controls. Rats subjected to a standardized splenic trauma had a 16% mortality when left untreated and a zero mortality with operative therapy by splenectomy, hemisplenectomy, or primary splenic repair. Hemisplenectomy and primary splenic repair are indeed feasible in rats with resultant splenic tissue showing a normal histologic appearance. Hemisplenectomized infant rats, when subjected to pneumococcal challenge, had a 15% mortality compared to 85% for splenectomized infant rats. This suggests that the repaired spleen retains its very important immunologic abiltiy to resist infection. Despite differences in species and organ sizes and shapes, these data suggest that partial splenectomy and primary splenic repair may be attractive alternatives to splenectomy in instances of trauma and inadvertant operative injury.