Sera from 33 children with and 84 without meningococcal disease were examined for antimeningococcal IgG and IgM antibodies using an ELISA test. The meningococcal patients had a significantly higher prevalence of specific IgG antibodies (p = 0.0014), and also higher prevalence of IgM antibodies (p = 0.08; NS) than other children. These results indicate that the patients had been immunologically stimulated for some time before admission. The meningococcal patients who died had lower prevalence of specific IgM antibodies than the surviving patients, but the difference was not significant (p = 0.16). A significant increase of or high level of antimeningococcal antibodies was found in 11/12 patients examined, the last one had high levels already at admission. This type of ELISA test should therefore be helpful in the diagnosis of meningococcal disease when blood or CSF cultures are negative.