The county of Cheshire, in its broadest, historical sense, has a rich diversity of wildlife, linked to a varied geology and land use. This is an account of a group of strange but fascinating organisms, the slime moulds, which straddle the boundaries between fungi and protozoans. After a short introduction to the biology and ecology of slime moulds, the physical and ecological environment of wider Cheshire is described. The main body of the work is a detailed catalogue of all the species ever recorded in the district. The records date back into the 19th century but are mostly concentrated in the last 40 years, since the author came to Chester. There are more than 90 maps, on a 5 km grid square base, of the commoner species.