Percentage of meningiococcal meningitis cases based on studies conducted over 39 years. Nine different studies were conducted on patients diagnosed with meningitis due to N. meningitids from 1965-2004. Between 1966-1989, meningococcal meningitis cases caused by serogroup A are only presented. In ES1965-1968conducted on 644 cases of ABM, it was reported that meningococcus was responsible for 56% of bacterial meningitis cases . In ES1966-1968on 187 patients, N. meningitidis was responsible for 49% of 123 culture positive cases and again identified as the leading cause of bacterial meningitis . The prospective study ES1966-1989 on 7,809 patients also reported that 54% of meningitis cases were caused by N. meningitidis . A retrospective study ES1971-1975 done on 1,333 patients reported that 56% of the cases were due to N. meningitidis infection . ES1971-1974, on 783 patients reported that 54.4% (426) of the meningitis cases were due to meningococcal infection . ES1977-1978 on 1627 CSF specimen demonstrated that N. meningitidis was the second most common bacterial meningitis (25.4% of the 350 bacterial meningitis cases) . In the ES1998-2000 on 2047 children less than 6 years, N. meningitidis was reported to be responsible for 13% of the 228 bacterial meningitis cases . The ES2000 identified N. meningitidis as the second leading cause of bacterial meningitis in Egypt responsible for 30% of the 223 patients positive culture . Prospective study ES2002-2003 on 310 children clinically diagnosed with meningitis detected N. meningitidis in 14.2% of the cases and documented it as the second leading cause . ES1998-2004 placed N. meningitidis as the third cause of bacterial meningitis . The asterisks represent epidemiological studies reporting an average during the entire period of the study.