We studied periventricular echodensities (PVE) in 154 premature infants under 33 weeks of gestational age. PVEs were classified into four groups due to Pidcock's description, and its relation with periventricular leukomalacia (PVL) was examined as a cause of cerebral palsy. Twelve (11%) of 112 infants with PVE 2 and all of 10 infants with PVE 3 were developed cystic PVL. PVE 3 was therefore considered to be the same as the pathological PVL. Infants of PVE 2 - 3 groups were more premature and lower in birth weight, and they were more often complicated with respiratory distress syndrome, asphyxia, recurrent apneic episode, patent ductus arteriosus and hypocarbia than those of PVE 0 - 1 groups. PVE 2 disappeared in patients with PVL later than in those without PVL.