Through the Danish National Patient Registry we identified all children 0-15 years old who had been splenectomized during the period 1979-87 and all children of the same age who, during the same period of time, had been admitted to a hospital because of either meningitis or bacteraemia caused by Streptococcus pneumoniae. We wanted to see whether any of the splenectomized children had developed invasive pneumococcal infection during the observation period. A similar Danish study covering the period 1969-78, when pneumococcal vaccine was not available, has already been published (3). Four per cent of the children splenectomized during that period developed invasive pneumococcal infection in contrast to none of the children splenectomized and vaccinated during the period 1979-87. Since 1982 antibiotic treatment of splenectomized patients running a fever has been recommended, and we show that the program of pneumococcal vaccination and defined antibiotic prophylaxis has been highly efficacious in preventing post-splenectomy infections in children.