Protecting millions of workers from occupational hazards frequently involves the use of respirators, protective clothing, gloves, or other personal protective technologies (PPT). For some occupations, such as firefighting, the worker's protective equipment is the only form of protection against life-threatening hazards, while for others, such as healthcare workers, PPT is one component in a series of protective controls. In conjunction with a series of planned reviews of National Institute for Occupational Safety and Health (NIOSH) research programs, the Institute of Medicine (IOM) and the National Research Council (NRC) convened a committee of experts to review the NIOSH Personal Protective Technology Program (PPT Program) to evaluate the relevance of its work to improvements in occupational safety and health and the impact of its work in reducing workplace illnesses and injuries. Relevance was evaluated based on the priority of work carried out and the strength and plausibility of its association with improvements in workplace protection. Impact was evaluated based on contributions to intermediate and end outcomes linked to worker health and safety. The committee was also asked to assess the program's targeting of new research areas, identify emerging issues in PPT, and provide recommendations for strengthening the program. In addition to reviewing the PPT research efforts, the committee's task included evaluating the respirator certification program and appraising the policy and standards development efforts of the PPT Program. Taking into account several important factors beyond the program's control, the committee found that since 2001 (the period covered by this review), the PPT Program has made meaningful contributions to improving worker health and safety. Using a five-point scoring scale (where 5 is highest), the committee assigned the NIOSH PPT Program a score of 4 for relevance. This score reflects the judgment that the PPT Program is working in priority areas and is engaged in transferring its research to improved products and processes. The committee also assigned the PPT Program a score of 4 for impact, indicating that the program has made probable contributions to end outcomes (improvements in worker health or safety) in addition to well-accepted intermediate outcomes. To enhance the relevance and impact of its work, the committee recommends the development of a National PPT Program consistent with the original congressional mandate that would foster the development of improved protection for all workers through coordinated oversight of all PPT. The committee also recommends that the PPT Program establish research centers of excellence, enhance the respirator certification process, increase research on the use and usability of PPT, and assess PPT use and effectiveness in the workplace using a life-cycle approach.