As we enter the last decade of the twentieth century, the AIDS epidemic looms ever larger and threatening. The specter of upwards of a million deaths in the United States and perhaps many millions worldwide from a sexually transmitted virus shakes our belief in modem medical science, while challenging the foundations of democratic society. Almost ten years into the epidemic, and with an enormous body of basic science research on the Human Immunodeficiency Virus (HIV), we still do not know why AIDS emerged when it did or how to stop its spread. A very humbling experience for scientists, clinicians, public health experts, politicians, and the general public. Yet there are signs that a well coordinated multidisciplinary research program can conquer the epidemic and, perhaps, provide the basis for preventing future epidemics. The HIV family of viruses is now better understood, both in terms of structure and function, than any other virus. Genetically engineered peptides and nucleic acids are being tested as specific treatments or vaccines against HIV infection/disease. Most prom ising are the strides which have been made in understanding those aspects of human behavior which have contributed to the spread of HIV infection and which must be substantially modified if AIDS is to be controlled and eventually eradicated. The basis of that understanding has roots in a diverse set of disciplines which have converged in the work presented in this book.