During a four-month summer period, 390 cerebrospinalfluid specimens from 357 patients were studied for the presence of a free-living amoebae.Naegleria gruberiwas cultured from one patient with lethal meningoencephalitis.Acanthamoeba astronyxiswas cultured from another patient with nonlethal meningitis. The latter represents, to our knowledge, the first case of nonlethal meningitis caused by the free-living amoebae. Fresh water was implicated again as a possible epidemiologic source. In any purulent meningitis in which bacteria cannot be demonstrated, amoebae should be looked for in the cerebrospinal fluid.