The purpose of the study was to assess reference ranges for lateral ventricular volume of very low birth weight (VLBW) infants using 3-D ultrasound (US). A total of 108 patients with birth weights < or =1500 g or mother's postmenstrual age < or =32 weeks were examined prospectively in a longitudinal study. Infants in conditions considered being potential confounders such as intraventricular haemorrhage (IVH) and periventricular leukomalacia (PVL) were not included in the calculations. Hence, 77 subjects remained for final statistical analysis. Mean postmenstrual age at birth was 194.5 (27 weeks and 5.5 days) +/- 14 SD days, mean birth weight was 972.5 +/- 236.3 SD g. Reference ranges for lateral ventricle volume were established from serial images. The exponential regression analyses revealed a weekly increase in volume of 6.3% (95% CI 4.4%-8.3%) and 6.6% (95% CI 4.7%-8.6%) in respect to the left and the right ventricle (p < 0.001). Postmenstrual age correlated significantly (p < or = 0.015) with ventricle volume. No significant association to head circumference could be determined. Establishment of reference values for the lateral ventricle volume of VLBW infants should facilitate application of 3-D US in routine diagnostics in neonatal intensive care units and detection of ventricular enlargement as a prediction of risk for poor neurodevelopmental outcome in high-risk cohorts.