The purpose of this publication is to provide a cross-sectional version of the present state of gnotobiology and its clinical applications by biomedical scientists and physicians. With contributions from abroad as well as from the United States, the current status of gnotobiology is amply explored. We wish to express our sincere appreciation to the participants for their contributions to this Symposium held in Buffalo, New York on June 9 - 11, 1968, sponsored by Roswell Park Memorial Institute, State University of New York at Buffalo School of Pharmacy, and the Association for Gnotobiotics, Inc. We owe a great debt to those pioneers who labored under great hardships to develop this area of science.