The principles and practices of research peer review are described. While the principles are fundamentally generic and apply to peer review across the full spectrum of performing institutions as well as to manuscript/proposal/program peer review, the focus of this paper is peer review of proposed and ongoing programs in federal agencies. The paper describes desireable characteristics and important intangible factors in successful peer review. Also presented is a heuristic protocol for the conduct of successful peer review research evaluations and impact (...) assessments. Problems with peer review are then outlined, followed by examples of peer review of proposed and existing programs in selected federal agencies. Some peer review variants, such as the Science Court, are described, and then research requirements to improve peer review are discussed. (shrink)