Back injuries remain the largest single cause of worker disability in the United States, with almost 280,000 lost workday back injuries reported in 1998. In response, workers and employees have adopted the use of back belts as a preventive measure, with approximately 4 million back belts purchased in 1995. Even though back belts have become common in many workplaces, scientific evidence of their effectiveness has been equivocal. Although there have been other studies to evaluate back belts, we describe the largest study using a prospective design based on individual data. A full description of this study was published in the December 6, 2000, issue of the Journal of the American Medical Association.