This comprehensive treatise on the reticuloendothelial system is a project jointly shared by individual members of the Reticuloendothelial (RE) Society and bio medical scientists in general who are interested in the intricate system of cells and molecular moieties derived from these cells which constitute the RES. It may now be more fashionable in some quarters to consider these cells as part of what is called the mononuclear phagocytic system or the lymphoreticular system. Nevertheless, because of historical developments and current interest in the subject by investigators from many diverse areas, it seems advantageous to present in one comprehensive treatise current information and knowledge con cerning basic aspects of the RES, such as morphology, biochemistry, phylogeny and ontogeny, physiology, and pharmacology as well as clinical areas including immunopathology, cancer, infectious diseases, allergy, and hypersensitivity. It is anticipated that by presenting information concerning these apparently heterogeneous topics under the unifying umbrella of the RES attention will be focused on the similarities as well as interactions among the cell types constitut ing the RES from the viewpoint of various disciplines. The treatise editors and their editorial board, consisting predominantly of the editors of individual vol umes, are extremely grateful for the enthusiastic cooperation and enormous task undertaken by members of the biomedical community in general and especially by members of the American as well as European and Japanese Reticuloendothe lial Societies."

This issue of Current Topics in Microbiology and Immunology records the proceedings of a Workshop on the Immunology of Sili cones held at the Natcher Conference Center, National Institutes of Health, Bethesda, Maryland, March 13 and 14, 1995. A large num ber of investigators from North America and Europe met to discuss available data on how the immune system responds to silicones and related materials. Some aspects of this field are controversial. Nonetheless, the meeting was marked by a civil and open ex change of scientific information and divergent interpretations, re flecting the traditions of scientific communication. Each invited participant was asked to submit an article sum marizing his/her presentation. Most of the papers are published as submitted, with only editorial changes to conform with the guide lines given to each contributor or revisions to clarify aspects of the paper. The papers should not be regarded as peer-reviewed publi cations. This preface will attempt to outline some of the immu nological areas of investigation relating to silicones."