The objective of this study is to compare the neurodevelopmental outcome between very low birth weight infants with and without sonographic disproportionate enlargement of occipital horn. We retrospectively reviewed the brain sonography of all very low birth weight infants born at National Taiwan University Hospital between June 1997 and June 1999. Brain sonography was routinely performed at the age of the third, seventh, twenty-first, and later days as clinically indicated. Intracranial hemorrhage, periventricular leukomalacia, congenital hydrocephalus, and Stage III retinopathy of prematurity were excluded from our study because of the association with neurodevelopmental impairment. Patients with disproportional dilatation of occipital horn more than 15 mm in width were included in the study group, and those with less than 15 mm were in the control group. Both groups received developmental evaluation by the Bayley Scales of Infant Development II at corrected age of 6, 12, 18, and 24 months, respectively. Socioeconomic status and detailed medical history were obtained at assessments. Independent-samples t test was used for comparison. A total of 81 very low birth weight infants were included in this study: 49 infants (female 18, male 31) in the study group and 32 infants (female 23, male 9) in the control group. The mean gestation in these two groups was 30 +/- 2 weeks and 31.1 +/- 2.2 weeks (P = 0.156), and the mean birth body weight was 1290 +/- 269 gm and 1282 +/- 219 gm (P = 0.877), respectively. At corrected age of 24 months, there was no significant difference in muscle tone, neuromotor impairment, hearing impairment, vision, or speech development. Assessment with the mental development index (88.9 +/- 15.6 vs 93 +/- 13.2) (P = 0.238) and the psychomotor development index (93.3 +/- 10.3 vs 89.6 +/- 12.1) (P = 0.149) between these two groups was also comparable. This retrospective analysis suggests that ultrasonographic disproportionate enlargement of the occipital horn in very low birth weight infants does not affect the neuromotor development at corrected ages of 6, 12, 18, and 24 months.