Eight of 67 patients became transiently aphasic after myelography or cisternography with metrizamide. All eight patients had been placed in the left lateral decubitus position for pluridirectional tomography. Immediate EEGs revealed focal left-sided abnormalities in two patients. In one other patient, a computed tomographic scan showed contrast mainly over the left hemisphere. All of the symptoms resolved within 48 hours. In 34 patients who were placed on the right side, no language disturbance was noted. Aphasia after pluridirectional tomography with metrizamide may be due to local irritation of the perisylvian language centers of the dominant hemisphere. The phenomenon is distinct from syndromes of generalized confusion. The complication may be avoided by placing patients in a right lateral decubitus position for pluridirectional tomography.