Future of HIV vaccine unclear

Puzzling hints of success require explanation before trials can move forward.

BRIEFING: US Senate gears up for climate debate

Cap-and-trade bill largely mirrors legislation passed in the House of Representatives.

Oldest hominid skeleton revealed

At 4.4 million years, Ethiopian fossil clarifies human–chimp relationships.

Q+A: The new head of the NIH

Francis Collins talks about his priorities for the agency.