The study traces the history and development of Loe Pool, a 50 hectare freshwater coastal lake near Helston, Cornwall. using a wide variety of palaeolimnological and associated research techniques. The principle upon which such research is based is that there is an intimate relationship between the history of a catchment and the lake into which it drains. In addition, the history of the shingle bar which now isolates Loe Pool from the sea is explored, as this has also had a significant bearing on the lake's physical and ecological development. The study uses a combination of lines of evidence to interpret the development of the lake-catchment system. Palaeolimnological techniques. employed include the examination of the physical nature of the lake sediments themselves, and chemical and biological analyses, in particular for sub-fossil diatoms. These are used to establish both a chronology of sediment deposition, and also a detailed history of the principal ecological changes experienced by the Pool. In addition, a considerable amount of historical documentary and cartographic 'material is incorporated in the study, in order to provide corroborative evidence of the major events that have taken place in the history of the lake and catchment. The results highlight the main influences on the lake, and in particular, those of the last two hundred years. Marine incursions dominated the lake's history up until the late 19th century, when both natural overspill of lake water and the customary practise by local residents of 'breaching the bar' ceased. Tin mining within the catchment has also had a major impact on the lake and has given rise to several periods of very rapid sediment accumulation, the most significant of which took place in the 1930's and 1930's. Following the cessation, in 1939, of all mining activity within the catchment, the discharge of treated sewage effluent, which had begun in 1930, became the dominant influence upon the lake's ecology. It is hoped that such an historical background will allow a more sympathetic management of the lake in future years.