In 1962 the Civil Engineering Research Association (CERA) sponsored laboratory tests which resulted in the publication of a report (1) giving design procedures for determining the riprap size required for given design wave conditions. the CERA work represents one of the first attempts to rel.te the results of tests using regular waves to those using irregular waves (laboratory wind generated in this instance) This relationship is a particular problem because most quantitative information on wave damage comes from laboratory generated regular waves rather than from irregular waves of the kind found in nature. Before an extension of the CERA work could be satisfactorily completed it became clear that the regular-irregular wave problem could be solved by using paddle generated, irregular waves which had meanwhile become available. Thus it was decided to take advantage of improved techniques and make a new series of tests which covered parts of hoth the original CERA research programmes, This report describes the tests and the resulting design procedures which apply to deep water waves .. Tn brief, the volume of riprap eroded was measured as a function of the number of incident Waves for each of three sizes of riprap for each of several significant wave heights at three mean wave periods. These measurements were made on slopes of J : 2, I : 3, 1 : 4 and 1 : 6 throughout the work, in the planning, execution and reporting, discussions were held with practising engineers who formed the majority of a steering group (Appendix I) set up by the Construction Industry Research and Information Association (CIRIA, successor to CERA) to guide the project