In the first study of its kind, researchers report today that so-called triple therapy for HIV-positive individuals can not only reduce blood levels of the virus, but also significantly slows the progression from infection to actual clinical symptoms of AIDS.

In a separate study, scientists also show that the combination of a protease inhibitor with two conventional antiviral drugs, AZT and 3TC, can keep AIDS virus levels low for as long as a year. Some experts had feared that the virus would become resistant to such combinations or that the drugs would lose effect over time.

The two studies in the New England Journal of Medicine provide strong confirmation that triple therapy is the best way to attack AIDS and that its use should be extended to the about two-thirds of America's 900,000 HIV-positive people who are not receiving it, experts said.