Premature birth is a factor of increased blood pressure in adulthood. Little is known about the physiologic characteristics of the arterial bed in neonates. The aim of this study was to characterize in vivo the arterial compliance in neonates and its maturation profile in very low birth weight (VLBW) premature infants. A group of stable, VLBW premature infants was compared with a control group of near term neonates. The abdominal aortic wall distensibility coefficient (DC) and whole-body arterial compliance (WBAC) were determined using specifically designed noninvasive methods, based on ultrasonic measurements in combination with synchronous, beat-to-beat recording of aortic pulse pressure (PP). On the fifth day of life, WBAC and the CD were lower in VLBW premature infants than in controls. Furthermore, WBAC and the DC remained unchanged in VLBW premature infants 7 wk after birth. In conclusion, VLBW premature infants are characterized as early as the fifth day of life by high arterial stiffness, which persists when they reach their theoretical term. It can be speculated that early alteration of arterial elastic properties may pave the way for long-term elevation of arterial pressure in VLBW premature infants.