This research evaluated empirically the effects of hand tool handle shape and size on the hand's capability to resist or exert force in six different orientations: thrust push, thrust pull, orthogonal push, orthogonal pull, wrist extension, and wrist flexion. Each test employed ten male and ten female subjects with a recent history of manual labor. Age ranged from 18 to 44 years, with an average of 26 for males and 28 for females. Thirty-six handles of four sizes and nine shapes were tested for maximum force exertion. All testing was conducted under slippery film conditions to eliminate the effect of the surface finish of the handles and to more accurately assess the inherent characteristics of each handle. Subjects were able to generate higher forces with different sizes and shapes of handles, depending upon the direction of force exertion. For tasks that involve a high percentage of thrust push or pull type activities, the authors conclude that triangular handles should be selected. If not feasible, rectangular handles may be substituted. In thrust type tasks, handles with square and circular cross sections are to be avoided. Handles may need to be smaller in circumference for women than for men. For tasks having a predominance of both orthogonal push and pull activities together, rectangular handles with a width to height ratio of about 1 to 1.25 appear to be the best compromise. For tasks with a high percentage of wrist extension and flexion, rectangular or triangular handles are best. For a tool that is used with all of the activities, such as a standard meat packing knife, rectangular handles appear to be a good compromise. The authors conclude that each handle is appropriate for a particular task, and may not be suitable for other tasks.