Neisseria meningitidis is an encapsulated Gram-negative diplococcus which colonises the upper respiratory tract without causing symptoms in up to 25% of the population. In the UK serogroup B causes more than 80% of cases of invasive meningococcal disease (IMD). Petechiae which start to spread, become purpuric, occur in association with signs of shock or meningitis, or in any child who appears ill should always be treated as IMD until proven otherwise. Any child with symptoms and signs suggestive of IMD and a non-blanching rash should be transferred to hospital as an emergency immediately. IM (or IV) benzylpenicillin (or ceftriaxone) should be given at the earliest opportunity, but treatment should not delay transfer. [With external links to the evidence base]