Background: The degree of periventricular white matter echodensity in preterm infants has been utilized as a sign of the early ultrasonographic appearance of periventricular leukomalacia, and this has been called periventricular echodensity (PVE). Objectives: The aim of this study was to quantitatively measure PVE utilizing a new method which is called calibrated integrated backscatter (calibrated IB). Methods: Eighty-eight preterm infants (extremely low birth weight infants, n = 17; very low birth weight infants, n = 26; low birth weight infants, n = 45) without any CNS abnormality were enrolled. IB is the returned sound pressure against supersonic waves sent from an ultrasonographic machine. The IB of the choroid plexus and periventricular white matter in the subrolandic area were measured on a parasagittal cerebral image. The degree of PVE was defined by subtracting the IB of the choroid plexus from that of the periventricular white matter in the subrolandic area (calibrated IB of PVE). Results: The intraobserver and interobserver correlations were both excellent (between 0.87 and 0.98 as correlation coefficients). There was a trend for the calibrated IB of PVE to decrease in accordance with time after birth, with a significant difference in very low birth weight and low birth weight infants. Conclusions: The objectively measured brightness of PVE was comparable to that of the choroid plexus irrespective of the size of the infants. Measurement of the calibrated IB of PVE might be a reliable method to assess PVE.