The pathogenesis of neonatal periventricular-intraventricular hemorrhage (PVH-IVH) remains unclear, although an aberration in cerebral hemodynamics imposed upon prematurity appears fundamental. Microthermistors were implanted in the cerebral cortex of 17 adult greyhounds. An analog-digital hybrid system developed using the IBM PC computer to provide simultaneous continuous 1CBF data at four discrete sites. Variables of peak inspiratory pressure (PIP), positive and expiratory pressure (PEEP), total minute ventilation and pulse pressure were investigated through a 1 mm burr hole as well as 2 cm craniotomy to compare cranial compliance effects. Positive pressure ventilation induces a fluctuating pattern of 1CBF with blood flow lowest during peak inspiration. A large craniotomy defect (simulating the open fontanel), high PIP or high PEEP accentuate this effect. The use of a small burr hole to simulate a closed fontanel results in the obliteration of the fluctuating pattern and the enhancement of beat-to-beat changes in 1CBF that were directly proportional to pulse pressure. These data suggest that hemodynamic changes produce fluctuations in local tissue perfusion which are dependent upon cranial compliance. The exact relation of such changes to the pathogenesis of PVH-IVH requires continuous 1CBF measurement in the subependymal zone in the human newborn or an animal model.