A large fauna and a large flora are described from terrace deposits of the River Salwarpe at Upton Warren, Worcestershire. The fossils occur in several extensive lenticular bands of silt in the lower half of a gravel succession. From the stratigraphy and a radiocarbon age of 42 000 years, the deposits are ascribed to the beginning of the Gottweig Interstadial, immediately following the maximum of the Midland Irish Sea Glaciation. The latter is thus considered to belong to the last and most severe episode of the Early Wurm. The silt bands represent a succession of ancient pools which contained an extensive fauna of vertebrates, molluscs, ostracods, insects and spiders and a large flora which call for explanation in ecological and climatological terms. The beetles include a substantial component not now British; there is a strong northern element but others are more southern in their present-day distribution, one or two are continental and at least three appear to be extinct. The flora is akin to that of present-day south Sweden except for a great scarcity of trees. There is evidence from several directions of the existence of brine springs, causing the water of one pool to be mildly brackish and affecting its fauna and flora. Some of the drier land plants also suggest a salty environment. Apart from this complication, the fauna shows an unexpected mixture of northern and less northern forms which nowadays would be mutually incompatible. This is explained as due to a very rapid amelioration of climate following the glacial maximum, with Arctic species still persisting against the inroads of the more thermophilous species coming from the south. The scarcity of trees is not ascribed to true tundra conditions but it is suggested that the grazing of large herds of bison may have had a controlling influence on tree growth.