Splenectomy, the removal of the spleen, is a relatively benign procedure with few immediate risks. On the other hand, in the long term, it has two important consequences: one, a transient increase in the number of platelets in the blood, and two, a decrease in the resistance of the immune system to certain infections, particularly those with pneumococci. This warrants routine pneumococcal vaccination prior to surgery and vigorous treatment of any onset of infection in subjects who no longer have a spleen.