The first 100 years of drug regulation by the US Food and Drug Administration (FDA) have been sculpted by a series of tragedies and the consequent broadening of the FDA's authority by Congress. The distinguishing feature of the FDA's execution of its mission is that it has routinely turned to science as the primary basis for decision making, and for this reason, it is one of the world's most respected regulatory agencies. Regulatory science, currently defined by the FDA as the science that underpins its decisions, has been the foundation for the FDA's success since its inception. This review focuses on the role of science as the basis for FDA decision making. It examines how regulatory science has made the FDA's past successes possible and concludes with an overview of how the FDA might augment its science-based regulation in the future and what new policy alternatives might be necessary.