Regional cerebral blood flow (RCBF) was measured in 17 newborn beagle puppies under conditions of moderate hypotension, normotension, and moderate hypertension. RCBF demonstrated autoregulation over the blood pressure range 35-70 mm Hg. When arterial pressure exceeded 75 mm Hg, RCBF increased significantly for all grey matter structures, 2 of 4 white matter structures, and 2 of 3 germinal matrix structures. The magnitude of the hypertension-induced increase in RCBF was highest for thalamic and mesencephalic nuclei, intermediate in cerebral cortex and other subcortical nuclei, and lowest in white matter. The hypertension-induced increase in CBF was low (similar to white matter) in some areas of germinal matrix but higher (similar to midline cerebral cortex) to rostral germinal matrix. The differences in RCBF during hypertension between rostral germinal matrix and cerebral white matter may partially explain the vulnerability of the germinal matrix to hemorrhage.