There is substantial evidence that the right brain is superior for the perception of space and form, while the left possesses greater language capabilities. One model of information processing based on the lateralized function of each hemisphere proposes that the brain operates most efficiently with direct access (lateralized input) of the appropriate task to each hemisphere (1, 2). The advantage achieved with lateralized input, however, may not persist when competing tasks draw on similar resources from the same hemisphere. The present study investigated the constancy of the lateral-input advantage on the secondary task of two tasks requiring resources from the same hemisphere. Thirteen dextral, male, experienced pilots performed a parafoveal, visuospatial task while maintaining bank and pitch control of a flight simulator, a dual-axis compensatorytrading task. Subjects maintained level pitch and bank on the attitude indicator of a heads-up display using both hands on the control stick. The secondary task stimuli 06 circles, squares, and triangles, high x wide, with the central edge displaced 2 from the center of the heads-up display, were presented for 66 msec. Each trial consisted of a .5-sec. tone, a l-sec. delay, a 66-msec. stimulus, a l-sec. delay, and a 66-msec. stimulus. Subiects depressed a trigger on the control stick only when the second figure of the stimulus pair matched the first. There were 60 test pairs in each visual field for a total of 120 trials. Half of the trials were matches, and half of the responses were made with the index finger of each hand. Order of visual-fields and hand responses were counterbalanced. Emphasis was placed on sacrificing the secondary task for aircraft attirude control. The mean correct reaction times for the four visual-field and hand-response conditions were for left field: left hand = 567 msec. (SD = 132) and right hand = 528 msec. (SD = 107); for right field: left hand = 602 msec. (SD = 137) and right hand = 558 msec. (SD = 91). A repeated-measures analysis of variance produced significant effects (p 4 .02) for visual half-field (PI.= = 8.21) and response hand (R.u = 11.79), but no interaction. Errors were too few for meaningful analysis. The left-field (right-brain) advantage was significant for both left- (tu = 2.37) and righthand (t~ = 2.54) responses. There was a right-hand advantage for both the left-field (t~? = 3.70) and the right-field (t~ = 3.70) viewing. The more rapid left-field RTs indicate that, independent of response hand, the visuospatial task was accomplished more efficiently in the right brain. This left-field (right-brain) superiority supports the notion that the lateralized input advantage for visuospatial tasks persists in a dual-task situation where both tasks draw on similar resources from the same side of the brain. The right-hand advantage mag be attributed to the pilots' considerable experience making both tracking and switching operations on aircraft control sticks with the right hand but not the left.