The epidemiology of serogroup X meningococcal meningitis in Africa is unknown. During a serogroup X meningococcus outbreak in Kenya, case finding involved record review at health facilities and interviews with health workers and community leaders in West Pokot district. An age- and location-matched case-control study for risk factors was done. From December 2005 to April 2006, 82 suspect cases of meningitis were reported; the epidemic threshold was surpassed within two administrative divisions. Most (58%) cases were 5-24 years old; the case-fatality ratio was 21%. Serogroup X meningococcus was the most common serogroup - 5 (63%) of eight isolates serogrouped. Living in the same compound as another case, preceding upper respiratory tract infection and cooking outside the house were significant risk factors for disease. Serogroup X meningococcus caused an outbreak with similar epidemiology and risk factors as other serogroups. Serogroup-specific laboratory-based surveillance for meningococcus in Africa to detect serogroup X disease should be enhanced.