Each day, several thousand U.S. workers sustain disabling injuries on the job, more than a dozen workers die from injuries suffered at work, and over a hundred workers die from work-related diseases. The strategic goals and objectives of the National Institute for Occupational Safety and Health (NIOSH) are to conduct research to reduce work-related illnesses and injuries and to promote safe and healthy workplaces. In 2004, NIOSH asked the National Academies to review its portfolio of research. This report is part of a series of reports issued by the National Research Council and the Institute of Medicine that assess the impact and relevance of the NIOSH research programs in improving occupational safety and health. The reports also discuss emerging issues relevant to research needed for future improvements in worker protection.