The National Science Foundation (NSF) asked the National Academies of Sciences, Engineering, and Medicine to conduct a quadrennial review of the NSF Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs, in accordance with a legislative mandate. Drawing on published research plus existing data, Review of the SBIR and STTR Programs at the National Science Foundation analyzes the effectiveness of NSF award selection process and postaward assistance; the effectiveness of the STTR program in stimulating new collaborations; the economic and noneconomic impacts of the programs; effectiveness of the programs in stimulating technological innovation and supporting small, new firms across the technological spectrum; and the role of the programs in providing early capital to firms without other significant sources of support.