There is abundant evidence that in non-anoxic brain tissue the blood flow is controlled mainly by the functional activity of the neurons. This enables the use of regional blood flow measurements for the localization and quantitation of events in the human brain which correlate to normal and abnormal mental activity. Measurements of regional cerebral blood flow (rCBF) by means of the 133Xe clearance technique have been demonstrated that the activity distribution in the normal resting brain shows a typical "landscape", with the highest activities in the premotor and frontal regions and the lowest in temporal and parietal ones. The resting pattern is readily changed by voluntary motor activity which gives a rolandic-postrolandic activity peak and by sensory stimulation which activates rolandic and prerolandic structures especially. Speech and reading activates the upper, anterior and posterior speech cortices, as well as the face, tongue and mouth area. Problem solving also activates premotor and frontal regions especially and, if visual activity is involved, the occipital pole is also activated. These normal patterns confirm by and large well known aspects of the functional anatomy of the human dominant hemisphere.