This report presents the results of the environmental monitoring programme carried out during 1987 by staff of the Directorate of Fisheries Research, Lowestoft. The monitoring programme supports the Ministry`s functions under the Radioactive Substances Act, 1960 (Great Britain-Parliament, 1960). The programme is set up to verify the satisfactory control of liquid radioactive waste discharges to the aquatic environment, and to ensure that the resulting public radiation exposure is within nationally-accepted limits. The monitoring is independent of similar programmes carried out by nuclear site operators as a condition of their authorisations to discharge radioactive wastes. This report also includes results of monitoring carried out on behalf of departments of the Scottish Office, the Welsh Office, the Department of the Environment for Northern Ireland [DOE (NI)] and the Channel Islands States. Where appropriate, the information presented is supplemented by results from our extensive programme of research into the behaviour of radioactivity in the aquatic environment. (author).