Four cases of alexia without agraphia were studied by 99m-technetium pertechnetate brain scan. Two types of increased uptake were seen. One was of the triangular type near the midline in the posterior view, said to characterize an infarction in the distribution area of the posterior cerebral artery. This was associated with the well-known clinical picture of alexia without agraphia accompanied by hemianopia and color-naming defect, and was confirmed by postmortem examination. The other type of pathologic isotope uptake, observed in three patients, was more laterally placed, in the basal part of the left occipital lobe, and did not reach the midline. In these cases the alexia was transient and not associated with color-naming defects.