Bacterial meningitis should always be suspected in a patient with headache, high fever and neck stiffness. The symptoms may also include decreased level of consciousness. The cause of acute meningitis must be established quickly and the treatment must be started immediately. As soon as the bacteriological aetiology is established, the treatment is directed according to the aetiology. Viral meningitis is much more common than bacterial meningitis, the symptoms are milder, and the disease seldom causes an impairment of consciousness. Slowly progressing meningitis can be the cause of general symptoms and impaired consciousness, even when neck stiffness is absent.