Acanthamoeba spp. are ubiquitous free-living protozoa found in a wide range of environmental niches. They are resistant to disinfectants, temperature variation and desiccation and are responsible for two recognised diseases in humans, granulomatous amoebic encephalitis and keratitis. Both infections are rare, although the latter is currently receiving more attention following the association between Acanthamoeba and the wearing of contact lenses. Laboratory diagnosis is unusual but not beyond the bounds of most routine clinical microbiology departments. In this review the various aspects surrounding the ecology, pathogenicity and laboratory detection of Acanthamoeba spp. are considered.