This volume summarizes the Proceedings of the fourth biennial Cancer Teaching Symposium held on March 7 and 8, 1970, at the University of Chicago Pritzker School of Medicine. The program was prepared by Drs. LAWRENCE ALLEN, MELVIN GRIEM, WERNER KIRSTEN, LEON JACOBSON, JOHN ULTMANN, ROBERT WISSLER, and STANLEY Y ACHNIN. The purpose of the Symposium was to present current advances in the area of lymphoma and leukemia to the staff and students of this medical center and to students and interested physicians from other institutions in the Chicago area. Like the other teaching symposia held in 1964, 1966, and 1968, this Symposium attracted over 450 physicians and scientists. In the course of one and a half days the audience had the opportunity to listen to the twenty-four invited speakers and to lively discussions. The formal presentations as well as discussions are recorded in these pages. This Teaching Symposium could not have been undertaken without the faithful assistance of the Program Committee, the Cancer Training Grant Advisory Com- mittee, the staff who recorded and transcribed the Proceedings, and the editorial assistants. We wish to thank the following for their efforts: DOROTHY A. WILLIS, Administrative Secretary for Institutional Cancer Training Grant, Dr. ROBERT L. HUNTER, Dr. ROBERT H. KIRSCHNER, Dr. ROBERT A. ORLANDO, Dr. STEPHEN STRUM, RANDOLPH HUGHES, JULIA KANT, GEORGIA MOHR, TERRY PEARSON, FRIEDA RANNEY, and CAROL REESE. This Symposium received financial support from the Cancer Training Program Tt2 CA 08077-04 and The Chicago Tumor Institute.