Normal right-handers mentally rotated letters flashed in the left or right visual fields under different conditions of working-memory load. In Experiment 1, the subjects held patterns of eight dots or sequences of eight letters in working memory, and these conditions produced a progressively increasing right visual field (RVF) advantage in rate of mental rotation relative to a control condition in which there was no load. Experiment 2 confirmed the shift toward increasing RVF advantage with a load of eight digits relative to two control conditions, one in which there was no load and another in which the subjects recalled digits before carrying out the mental rotation on each trial. These results are discussed in terms of the priming of the hemispheres by the concurrent loading of working memory.