The goal of this study is to follow a prospective cohort of 1000 workers in two industries to evaluate the relationship between work-related risk factors and the development of non-traumatic soft tissue musculoskeletal disorders of the upper extremities (WMSDs). Musculoskeletal injuries and illnesses account for a tremendous amount of lost workdays and cost to industry in the United States. In this study, two hypotheses will be tested: The presence of the workload factors of hand force, awkward postures of the neck, shoulder, forearm, hands and wrists, and the repetitiveness of the work performed will cause an increase in the incidence of upper extremity work-related musculoskeletal disorders while controlling for individual and psychological factors. The interaction between the workload factors of hand force, awkward postures of the neck, shoulder, forearm, hands and wrists, and repetitiveness of the work performed will increase the risk of developing an upper extremity work-related musculoskeletal disorder. Nationally in 1998, there were 253,300 disorders associated with repetitive motion resulting in lost time including 26,000 cases of carpal tunnel syndrome and 22,000 tendon-related disorders (BLS, 1999) reported by private industry. The National Institute for Occupational Safety and Health (NIOSH) reported that about 700,000 (32 percent) of the cases involving lost workdays annually were attributed to repetitive motion disorders or overexertion (NIOSH, 1997). These reported injuries and illnesses result in a tremendous amount of lost productivity and a detrimental impact on the working and non-working lives of many people. Reducing workplace illnesses and hazards is the first priority of the Washington State Department of Labor and Industries. This research will be conducted in one manufacturing industry and one service industry, with multiple sites of each possible. SHARP surveillance activities using workers compensation data have identified manufacturing and service sector industries with high incidence of WMSD claims.