Subclasses of IgG antibodies to pneumococcal polysaccharide serotype antigens 4, 6A, and 23F were measured before and 4 weeks after vaccination with pneumococcal vaccine in young individuals splenectomized because of trauma and in a control group. An ELISA technique was applied. IgG2 anti-pneumococcal antibodies predominated before vaccination, especially against serotypes 4 and 6A. The youngest individuals in the splenectomy group tended to have lower IgG2 anti-pneumococcal antibody levels than the older ones. Vaccination induced antibodies of the IgG1 and IgG2 subclasses, and in some individuals also of the IgG4 subclass. Splenectomy does not seem to influence the IgG subclass pattern of antipneumococcal antibodies.