Linear hyperechogenicity (LHE) within the basal ganglia and thalamus is an uncommon sonographic finding in preterm infants and is of unclear significance. The study objectives were to determine the clinical characteristics and neurodevelopmental outcome in preterm infants who develop LHE. Ten preterm and 20 control infants were evaluated developmentally at 18 months adjusted age using the Bayley Scales of Infant Development. LHE was diagnosed at 4 weeks (range = 1-11). Antenatal glucocorticoid therapy was more common in infants with LHE than in the control infants (90% vs 45%). Four (44%) of nine LHE infants and no control infants were positive for cytomegalovirus (P = 0.02, and three of 10 LHE infants and no control infants had a hypothyroid (P = 0.03). The mental development scores and behavioral evaluation results were lower in the infants with LHE than in the control infants (73.7 +/- 9.7 vs 83.7 +/- 9.4, P = 0.01 and 23.7 +/- 20.1 vs 43.9 +/- 25.4, P = 0.04, respectively). The infants without LHE also had poorer motor quality (22.8 +/- 20. 5 vs 55.7 +/- 37.4, P = 0.02) and lower emotional regulation scores (25.7 +/- 16 vs 42.3 +/- 24, P = 0.06) than the control infants. Preterm infants with LHE are at an increased risk of adverse neurodevelopmental outcome and, in particular, cognitive and behavioral performance. The sonographic evolution of LHE may be a marker of a diffuse insult to the brain.