For approximately three decades, researchers have utilized psychophysics to develop guidelines (weights, forces and frequencies) for manual materials handling tasks. Early work by Stover Snook and his colleagues provided the foundations of the experimental methodologies that would be used by other researchers as well as design data that would be used by practitioners. Currently, there are extensive psychophysical data for designing a variety of materials handling tasks. The current state of psychophysical data will be examined, and the psychophysical approach will be compared to the biomechanical and physiological approaches to setting limits for materials handling tasks. The advantages and disadvantages of the psychophysical approach will be discussed, as will the research needs required to address the current limitations of the psychophysical approach.