HIV can be divided into two major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). HIV-1 is related to viruses found in chimpanzees and gorillas living in western Africa, while HIV-2 viruses are related to viruses found in the endangered West African primate sooty mangabey. HIV-1 viruses may be further divided into groups. The HIV-1 group M viruses predominate and are responsible for the AIDS pandemic. Group M can be further subdivided into subtypes based on genetic sequence data. Some of the subtypes are known to be more virulent or are resistant to different medications. Likewise, HIV-2 viruses are thought to be less virulent and transmissible than HIV-1 M group viruses, although HIV-2 is known to cause AIDS.

In the present book, thirteen typical literatures about drug resistance of HIV-1 published on international authoritative journals were selected to introduce the worldwide newest progress, which contains reviews or original researches on medical science, virology, epidemiology, ect. We hope this book can demonstrate advances in drug resistance of HIV-1 as well as give references to the researchers, students and other related people.