This study was designed to test the hypothesis that systemic hypotension during the first postnatal week increases the risk of ultrasonographic echolucency in the white matter of preterm infants (< or = 28 weeks' gestation) while adjusting for confounders. From a study base of 1607 very-low-birthweight neonates (500 to 1500 g), a subsample of 243 preterm infants (122 females; < or = 28 weeks' gestation) was selected for echolucency and data collection prospectively for the entire first postnatal week. Data analyses were performed separately for the first 24 hours of life, for the interval from the end of the first 24 hours to the end of the fourth postnatal day, and for days 5, 6, and 7. Systemic hypotension was defined as the mean arterial blood pressure in the lowest quartile for the infant's week of gestational age. Protocol cranial ultrasounds were those obtained closest to days 1, 7, and 21. A committee of sonologists classified the infants as having either echolucency (echolucency group) or not (control group). Systemic hypotension during the first week of life appeared to be associated with echolucency in univariable analyses but the association did not persist after adjustment for potential confounders. Detailed summaries of 13 previous studies, the majority of which did not show an association between systemic hypotension and white-matter damage, are presented. In sum, these results do not support the hypothesis that systemic hypotension contributes to echolucency among preterm infants.