Pneumococcal infections are still a cause of high morbidity and mortality in elderly populations. Since antibiotics are not wholly effective, vaccination should be performed. The response to pneumococcal vaccination of a limited group of elderly persons aged 60 to 90 years was studied. The sera of most individuals were found to contain antipneumococcal antibodies prior to vaccination. Vaccination resulted in antibody level increases in sera of all subjects except two. On the basis of antibody levels, 19 out of 20 vaccinees proved to be protected after vaccination. Combination of vaccination with a non-specific immunostimulation enhanced the antibody response.