Germinal plate hemorrhage with intraventricular rupture has been a leading cause of morbidity and mortality among premature neonates. Because germinal plate hemorrhage decreases with increasing gestational age, germinal plate vessel size and/or structure may be an important etiologic factor. Electron micrographs of the cortical and germinal plate blood vessels from 13 premature infants ranging in age from 19-37 weeks gestation were studied; vessel, lumena, and endothelial areas were measured using a digitizing tablet. In infants between 25-32 weeks gestation, the germinal plate vessel and lumenal areas were significantly greater than the areas of cortical vessel and lumena. This finding suggests that one of the factors involved in germinal plate hemorrhage is described by LaPlace's law which states that the larger the vessel diameter, the greater the pressure on the vessel wall.