Chemical analysis of stream, river and rainfall samples for lowland rivers in the UK. The data are uncensored and provide a basis for research purposes, and must be viewed in this light. Information on analytical methodologies is available, including detection limits, from which the user can choose how the data might be interpreted. The basins studied were the Tweed, Wear, Humber, Great Ouse and Thames. One tributary (the Teviot) and two main-stem sites were monitored in the Tweed Catchment. One site around two-thirds down the catchment of the River Wear was monitored. Humber Basin Monitoring was undertaken for all the tributaries especially near their downstream limits. The Great Ouse was monitored around half way down the catchment. The Thames catchment was monitored upstream and downstream of sewage inputs to the river, prior and post effluent stripping of phosphorus. This work formed part of a major UK initiative introduced in the early 1990s, the Land Ocean Interaction Study, LOIS, to examine water, chemical and sediment fluxes from the eastern UK rivers to the North Sea. The entire LOIS core monitoring data, including a wider range of determinands, is available from EIDC. As part of this and subsequent work, the initiative was extended to examine a range of catchment basins, from rural to agricultural and industrial/urban impacted ones.