A prospective ultrasound study was conducted in 179 normal pregnant women with gestational ages ranging from 15–40 weeks. Several biometric measurements were obtained throughout pregnancy, including the cerebrofrontal horn distance of the lateral ventricle, the frontal hemispheric width, and the calculated ratio of cerebrofrontal horn distance/hemispheric width. Curvilinear relationships were found between cerebrofrontal horn distance and gestational age (R2=0.597;P< .0001) and between cerebrofrontal horn distance and the biparietal diameter (R2=0.618;P<.0001). In addition, a curvilinear relationship existed between cerebrofrontal horn distance/hemispheric width ratio and gestational age (R2=0.492;P<.0001) and biparietal diameter (R2=0.930;P<.0001). These data represent a comprehensive characterization of normal growth of the fetal frontal horns. They provide a method by which variations from the norm can be assessed and early prenatal diagnosis of developmental anomalies of the fetal ventricular system can be made.