Infections caused by small, free-living amebas are still unfamiliar to many clinicians, pathologists, and laboratorians. As of 31 July 1989, more than 140 cases of primary amebic meningoencephalitis caused by Naegleria fowleri and more than 40 cases of granulomatous amebic encephalitis caused by Acanthamoeba species (including two cases in patients with AIDS) and possibly by other free-living amebas had occurred worldwide. The recent increase in acanthamoeba keratitis (more than 200 cases), especially in contact lens wearers, has generated new interest in this group of amebas. Effective treatment is still lacking. Risk factors, clinical manifestations, and laboratory parameters helpful in the recognition of infections of the central nervous system (i.e., granulomatous amebic encephalitis and primary amebic meningoencephalitis) and acanthamoeba keratitis are reviewed.