Early ultrasound examination can provide accurate antenatal diagnosis of many fetal congenital abnormalities but it is often difficult to translate this into prognosis because of the variable functional effects of similar anatomical changes. In the case of isolated fetal ventriculomegaly it is the prognosis that parents require in order to choose between continuing with the pregnancy or termination. The outcome for antenatally diagnosed ventriculomegaly seems to be worse than that reported in the neurosurgical literature for children treated with congenital hydrocephalus. Follow-up is available for 276 cases with apparently isolated ventriculomegaly who did not undergo termination of pregnancy. One hundred ninety-four (70 per cent) survived and of these 114 (59 per cent) had normal developmental quotient to follow-up. Intrapartum cephalocentesis to aid vaginal delivery is almost invariably associated with fetal/neonatal death. A favorable outcome of normal mental development is present in cases with borderline, stable (nonprogressive) isolated ventriculomegaly or cases in which ventriculomegaly has resolved in utero. Fetal surgery would seem to offer no benefit. The outcome is much worse when other associated congenital anomalies are present.