Splenectomy is a necessary remedial operation in a number of conditions in childhood; in others it is of questionable value. In traumatic rupture of the spleen, the necessity for removal of the organ is absolute and immediate; in aplastic anemia there is little need for haste and the possible benefit of the operation is doubtful. Between these extremes, there are several gradations (Table I). In the last 12 years, attention has been called to the greater frequency of sudden overwhelming infection in the splenectomized infants or children as compared to those with intact spleens. There are conflicting opinions about this danger. Some see no greater risk after splenectomy than after appendectomy; many others believe that the hazard is so specific as to contraindicate splenectomy in childhood, even when it might relieve acute or chronic hemolysis. The syndrome of overwhelming postsplenectomy infection (OPSI) is unlike most fulminating bacteremias and septicemias in ordinary (spleen-containing) individuals. Very few patients with bacteremia progress from good health to death in less than 24 hours, whereas the OPSI syndrome constitutes a distinct entity which often lasts only 12 to 18 hours. It may begin abruptly with slight sore throat, fever, and "feeling or looking sick," proceed to headache, vomiting, and hyperpyrexia; and be followed within a few hours by convulsions or coma and death. In the uncomplaining infant, the prodromata of spreading infection may be absent or missed. The pneumococcus is usually the invading organism. The meningococcus or influenza bacillus have also been blamed, but these infections last several days and are less fulminant.