This episode covers one half of the 2008 Nobel Prize in Physiology or Medicine, which was awarded to Luc Montagnier and Françoise Barré-Sinoussi. The Nobel Assembly at the Karolinska Institute chose to give Montagnier and Barré-Sinoussi the award “for their discovery of human immunodeficiency virus”. Topics include how the AIDS pandemic unfolded at the start of the 1980s, the work scientists did to discover the virus behind the pandemic, the ongoing search for an HIV vaccine, and some of the novel strategies scientists are testing to find a cure for HIV infections.