We measured changes in regional cerebral blood flow (rCBF) induced by reading, naming, and the Stroop effect in 12 right-handed normal volunteers. rCBF was quantified with a single-photon emission computerized tomograph after intravenous injection of 133Xe. Data were analyzed using predetermined regions of interest and a linear model. A significant relative activation was revealed in the right superior mesial frontal region during the Stroop effect.