A cement grout curtain has been formed in the North Abutment bedrock of Kielder Dam in Northumberland. In order to gauge the effectiveness of the grouting, a series of pre- and post-grouting Lugeon water tests were conducted in special control holes. This programme was executed according to proposals made in this journal on Lugeon testing (Houlsby 1976), which have now gained world-wide acclaim and acceptance. The paper demonstrates clearly both the practicality of the method and the usefulness of the results. Safe grouting pressures were selected following hydrofracture tests, again using similar methods. Data on curtain grouting design, execution and analysis are also provided, and fundamental observations made on the relationship of water takes and cement grout consumptions.