It would have been difficult at the beginning of the 80's to have predicted that by the end of the decade, Medical Virology would have become one of the most important topics in the area of both basic and clinical research. Although we were expecting a progressive increase in awareness of the role played by viruses in different diseases, we did not expect the outbreak of a fatal disease that was going to shake the roots of our society. The appearance of the human immunodeficiency virus (HIV-1) in the early 80's, has prompted a unique re search impetus in the area of Medical Virology. The knowledge that we are gaining in our attempt to understand the biology of HIV-1 and the immuno logical response to this virus should not only help us control the spread of this virus, but should also help us to better understand other viral infections. Let us hope that during the 1990's we can learn how to control HIV-1 infections so that by the end of the decade, no more human lives succumb to an infection with this virus. Luis M. de la Maza Irvine, California Ellena M. Peterson March, 1990 v ACKNO EDGEMENTS We would like to thank all the speakers that came to San Francisco and shared their knowledge during the lectures and for writing the chapters in this book."