The transition from text-oriented software to graphically-based software has brought about a rapid increase in the number of mouse users. Recently, increased usage of the mouse has been linked with the development of cumulative trauma disorders. This investigation concerns the effects that mouse surface height and wrist support have on wrist posture. Distance between targets and target width were varied to determine performance time and performance accuracy throughout the conditions. Results showed that the presence of a wrist support decreased wrist extension and radial deviation, and increased wrist flexion. However, wrist support had no significant effect on ulnar deviation. There was a significant interaction of support and surface height for wrist extension. Surface height had a significant effect on all dimensions of wrist posture. Higher surface height resulted in increased flexion and ulnar deviation, and decreased extension and radial deviation. Distance between targets was a significant effect for ulnar deviation. The long distance resulted in a greater amount of ulnar deviation. Accuracy was significantly affected by distance between targets and target width. There was a significant interaction of distance and width for flexion. When distance between targets and target width were converted to Indices of Difficulty (ID), it was found that as ID became larger, movement time between targets became longer (as predicted by Fitts' Law). / Master of Science