The relative importance of life sciences in spaceflight depends on the nature of the: mission. For brief missions to low earth orbit, such as Shuttle flights, issues involving health concerns, life support, or crew factors present fewer challenges than would longer flights, e.g., those planned for Space Station. For missions of exploration, such as a Mars expedition, the life sciences are not only important to the safety and success of the mission, they are on the critical path to being able to embark on the mission at all. This paper presents a brief history of the role of life sciences in the space program and describes the characteristics of exploration missions that impact life sciences requirements. It concludes by outlining what needs to be done if the very demanding life sciences requirements of exploration missions are to be supported.