In the quarter-century since the first report of AIDS in the United States, HIV infection has spread throughout the population, disproportionately affecting black women, Hispanic women, and men who have sex with men. The prognosis for persons infected with HIV has improved dramatically with the introduction and evolution of highly active antiretroviral therapy (HAART). The underlying principle of HAART is that a combination of potent antiretrovirals, each of which requires different mutations in the HIV genome for resistance to develop, can suppress replication sufficiently to prevent mutation and the emergence of resistance. The prospect that currently available antiretroviral therapy (ART) regimens may suppress HIV replication indefinitely provides the hope that infected patients will have life expectancies similar to those of age-matched uninfected individuals. For these patients, HIV care has shifted from an emphasis on treatment and prevention of the complications of HIV disease itself to a focus on suppression of HIV replication and management of short- and long-term complications of HIV, ART toxicities, and aging. This chapter describes the epidemiology, pathophysiology and pathogenesis, prevention, diagnosis, and management of acute and chronic HIV infection and AIDS, with figures and tables illustrating each chapter section. This review contains 9 figures, 32 tables, and 249 references