The Independent Radiation Monitoring Scheme for Clwyd began its monitoring programme in Clwyd in 1988. This is the fourth report on the results of the radiation monitoring carried out within Clwyd. The historical reasons for the conception of the Radiation Monitoring Scheme are given in the First Annual Report together with the protocol of operation and detailed sampling and monitoring information. The fourth Annual Report identifies any changes in techniques that have occurred in the last twelve months together with the latest monitoring and analytical data. Samples of air, beach materials, coastal sand and silt, seaweed, meat, fish and milk were taken from various locations within the county. No significant charges in radiation levels were found when compared with data from previous years. The values have remained within the range currently being expected throughout the United Kingdom. (author).