Left-sided unilateral spatial agnosia has been considered to be a symptom which is produced by the damage in the right temporo-parieto-occipital junctional area. A regional cerebral blood flow (CBF) study was performed on 3 patiets having left-sided unilateral spatial agnosia by single photon emission computed tomography (Emission CT). Localization of lesions have been discussed.     Case 1 : a 69-year-old right-handed man. A CT scan revealed an area of low density in the total territory of the right middle cerebral artery. An Emission CT showed reduction of CBF in its territory including the temporo-parieto-occipital junctional area.     Case 2 : a 65-year-old right-handed woman. A CTscan showed right putaminal hemorrhage. An Emission CT revealed an ischemic area of the putamen with a surrounding white matter. It also shows an ischemic area of the posterior parietal lobe and the parieto-occipital junctional area.     Case 3: a 70-year-old right-handed woman. Cerebral angiography showed the right posterior cerebral artery occlusion in its crural segment. A CTscan revealed an area of low density in the right thalamus and medial portion of the occipital lobe. An Emission CT showed, however, a reduction of CBF in the total area of the right posterior cerebral artery including the parieto-occipital junctional area.     Localization of lesions common to the 3 patients obtained from the Emission CT is the right parieto-occipital junctional area. This area is suggested to have been the site of lesions producing left-sided unilateral spatial agnosia.