Each year, approximately 5,000 fatal work-related injuries and 4 million non-fatal injuries and illnesses occur in the United States. This number represents both unnecessary human suffering and high economic costs. In order to assist in better evaluating workplace safety and create safer work environments, the Institute of Medicine conducted a series of evaluations of the National Institute for Occupational Safety and Health (NIOSH) research programs, assessing the relevance and impact of NIOSH's work on improving worker safety and health. The reports also discuss emerging issues relevant to research needed for future improvements in worker protection.