A conceptual mathematical model of work related carpal tunnel syndrome (CTS) useful for establishing guidelines for preventing CTS was discussed. The authors postulate that friction between the tendons and tendon sheathes in the carpal tunnel is the most important factor for initiating or aggravating tenosynovitis which is regarded as a precursor to CTS and that the frictional energy is proportional to the product of the internal force required to do the work, the repetitiveness of the movements, and the wrist angle. Preventing the initial tenosynovitis could prevent CTS. Assuming that hand or wrist pain is associated with compression of the median nerve, it was further postulated that preventing the onset of hand pain or discomfort would prevent tenosynovitis and CTS. A mathematical equation describing the internal musculoskeletal forces exerted by the finger/hand/wrist/forearm complex, the repetitiveness of the task cycle per unit tine, and the wrist angles that must not be exceeded for a specific task to prevent wrist or hand pain was derived. The values for the internal musculoskeletal forces, task repetitiveness, and wrist angles could be obtained from controlled human experiments. The authors conclude that the model can be used to establish quantitative guidelines for preventing job related tenosynovitis and CTS.