The first step in addressing any problem is recognition of the problem and a measure of its size and scope. There have been few reviews to date of the evidence of a musculoskeletal disorders problem in construction, particularly in the United States. Construction contractors in the United States have questioned the existence of a musculoskeletal disorders problem in construction, so a review of the evidence is warranted. The types of evidence reviewed include: 1) historical evidence, 2) injury data, 3) workers' compensation data, 4) medical exam data, 5) survey data, and 6) exposure data. Injury data generally represent injuries that the employers have identified as work-related and recorded or reported. Workers' compensation data are from cases that have been filed by workers for compensation and quite often represent only "closed" cases where compensation has been awarded. Medical exam data are from physical examinations of workers. Symptom survey data are the most inclusive and show the number of workers who self-report musculoskeletal problems. Exposure data include measurements made of exposure to musculoskeletal risk factors. The existing data show construction workers to be at significant risk of musculoskeletal injury, specifically related to the work they do. Their risk of musculoskeletal injury is much higher than that of other workers who have less heavy work, about 50 percent higher than all other workers. Several trades have been extensively studied, while others have been studied to a lesser extent. While the exact relationship between exposures and injuries is complex and often multifaceted, it would be difficult to deny the existence of the problem and the fact that these injuries are, to a great extent, related to the work that construction workers perform.