The crayfish records in this dataset are fom three main sources. 1) Records were submitted to the Biological Records Centre as the result of a project funded by English Nature (formerly the Nature Conservancy Council) and the Environment Agency (formerly the National Rivers authority). The project was carried out at Nottingham University by Dr David Holdich, David Rogers and Ian Reeve. This dataset includes field records and records derived from published sources. They cover the period 1900 to 1996. The records have been verified by Holdich and his co-workers and subject to routine validation by BRC. 2) Records were collated from the Enviroment Agency by Peter Sibley in 2003. Records were extracted from EA files that had been collected during crayfish surveys by Agency staff, and from other sources. Records were also extracted from the EA macroinvertebrate database of samples collected by Agency staff in the field. This dataset covers the period 1900 to 2003. Records were verified by Agency staff and have been subject to routine validation by BRC. 3) A small additional dataset of Environment Agency records from the EA Northumbrian Region has been added. Uploaded 14th July 2004.