A major design aspect of touch tablet operation is the display/control (D/C) gain. The primary objective of this research was the development and optimization of a variable D/C gain to improve human performance with touch tablets. This variable gain minimizes the speed-accuracy trade-off problem associated with traditional D/C gains. An additional objective.of this research was to determine the effect of tablet size on human performance. Display/control (D/C) gain is defined as the amount of movement which occurs on the display in response to a unit amount of movement of the control. With traditional D/C gains, there is a trade-off between low D/C gain which enables fine positioning, but results in very slow cursor movement, and high D/C gain which produces quick cursor movement but results in poor fine positioning ability. A lead-lag compensator which ameliorates this trade-off problem was developed. A lead-lag compensator is composed of a pure position gain component plus an additional velocity gain component. The results indicate that a lead-lag compensator greatly increased the target acquisition rate relative to a traditional D/C gain system. Percentage error increased with lead-lag compensation relative to an uncompensated system. The overall error rates were very low in all cases, however. Tablet size did not appear to significantly affect performance; performance on the three tablet sizes was generally consistent. / M.S.