The effect of 6"s rotary acceleration upon choice reaction time (RT) to an accelerating target in peripheral vision was the central issue in the experiment, with the level of acceleration and the viewing angle of the visual target as variables Twelve pilots were tested in a rotation device under conditions of visual stimulation alone and visual-plus-rotary stimulation The pilots responded to the direction of the visual motion by moving a hand controller to the right or left Visual-plus-rotary stimulation produced longer choice RTs than the visual stimulation alone Choice RT was inversely related to the level of acceleration and directly proportional to the viewing angle The findings are discussed in connection with theories of double stimulation and mtersensory effects