The SBIR program allocates 2.5 percent of 11 federal agencies' extramural R&D budgets to fund R&D projects by small businesses, providing approximately $2 billion annually in competitive awards. At the request of Congress, the National Academies conducted a comprehensive study of how the SBIR program has stimulated technological innovation and used small businesses to meet federal research and development needs. Drawing substantially on new data collection, this report provides a comprehensive overview of the SBIR program at the five agencies representing 96 percent of program expenditure--DOD, NIH, NSF, DOE, and NASA--and makes recommendations on improvements to the program. Separate books on each agency will also be issued.