1 2 J. H. SCHROEDER and B. H. PURSER 1 Introduction A symposium convened during the Vth International Coral Reef Congress in Papeete, Tahiti, 1985, encouraged the editors to assemble this volume of case studies by participating and, especially, by nonparticipating scientists. An attempt was made to include case studies from various regions and geological periods, carried out on various scales from regional to ultrastructural. We hope to present an overall view of reef diagenesis. Although the volume focuses on reef diagenesis, fields also to be considered are biology, paleontology, and sedimentary facies distribution, as they provide the context and, to some extent, encompass the determinants of diagenetic processes. The scope has been limited to reef diagenesis because we feel that reefs have relatively clearly defined geometries, which facilitate the evaluation of diagenetic trends and the definition of diagenetic models. On the other hand, their many different components make reefs somewhat more complex than other deposits, and this creates difficulties in deciphering diagenetic histories; the study of reefs, therefore, is not the simplest manner of solving the many problems relating to carbonate diagenesis. An additional reason for evaluating reef diagenesis is the reservoir potential of these carbonate bodies. To illustrate the point, in the recent collection of 35 case studies of carbonate reservoirs (Roehl and Choquette 1985), reefs were involved in 15. The emphasis on porosity development in many studies of the present volume is therefore not of mere academic interest.