This volume presents the Proceedings of the University of Chicago's third Cancer Training Grant supported Teaching Symposium. This Symposium received much of its support from grant number T12 CA 08077-02. Most of the planning of the Symposium and most of the local editing of the Proceedings was carried out by Dr. R. J. Michael Fry of the A.E.C. Argonne National Laboratory and by two members of the Advisory Committee of the Cancer Training Grant, Drs. Melvin Griem and Werner Kirsten. They carried the main responsibility for the Symposium. The subject of the Symposium, "Normal and Malignant Cell Growth," was chosen because, as the Proceedings reflect, it is a rapidly advancing field of endeavor which is of utmost importance to the understanding of the processes of malignant neoplasia. In fact, there is increasing evidence that knowledge of the kinetics of the cancer cell will greatly influence approaches to cancer therapy. Like the first two of these Teaching Symposia held in 1964 and 1966, this one attracted about 400 students and staff from this medical institution as well as from other medical centers in the Chicago area. The effective interplay of an excellent group of scientists with a lively and responsive audience was evident as they considered together a topic of great current interest in the field of neoplasia. Much of the credit for the smooth organization and implementation of the Symposium must go to Mrs.