Since 1996, combination therapies with antiretroviral drugs have been shown to increase length of life in many people with AIDS. (Drugs that suppress HIV, the virus that causes AIDS, are called antiretroviral drugs.) Combination therapy usually consists of taking three or four drugs of different types at the same time. Each of these drugs works in a different way against HIV. Combination therapy for AIDS is commonly called highly active antiretroviral therapy, or HAART. Currently, patients with newly diagnosed AIDS routinely receive HAART. Although we know that HAART can extend life for many of these patients, we do not know whether or how much HAART helps patients with severe or advanced, late-stage AIDS.