The present volume contains the first half of the edited tran script of a six-day Conference, "Fundamental Data on Reactions of Vascular Tissue in Man," held April 19-25, 1970, in Lindau, West Germany. The remainder of the proceedings, dealing with the epide miologic, clinical and preventive aspects of arteriosclerosis, will be published in a second volume. The Conference was held under the auspices of the International Society of Cardiology, the International Cardiology Foundation and the European Atherosclerosis Group. The aim of the Conference was to achieve a synthesis of present knowledge concerning arterioscle rosis. Therefore, workers were brought together from several coun tries and from various disciplines that do not ordinarily intercom municate for free exchange of data and ideas. Six broad subject areas were introduced by single papers; three of them are included in this volume. In the discussion which followed each formal pres entation, the participants attempted to reconcile disparate data and interpretations and to reach .a clear identification of important areas of ignorance and of crucial questions for future research. The format of the proceedings does not follow precisely that of the Conference itself. The formal papers are included, somewhat ab breviated, and excerpts of the discussion have been gathered under a series of topics arranged in logical sequence. Therefore, the quoted statements do not necessarily appear in order or in the place in the program where they were made. Principal issues, syntheses and unanswered questions are interspersed among the topics as edi torial comments.