BACKGROUND A fetal ultrasonographic (US) finding of mild ventriculomegaly (MVM) is not uncommon, but its prognostic significance is not clearly defined. OBJECTIVE To evaluate the clinical and US characteristics and outcome of fetuses with mild dilatation of the cerebral lateral ventricles. METHODS We reviewed the medical records of 34 consecutive fetuses with US evidence of MVM (atrial width of the lateral ventricles = 10-15 mm) at 18-35 weeks of gestation. RESULTS Of the 34 fetuses with MVM, 7 underwent karyotype examination and were normal. In 4 of the 34 fetuses the pregnancy was terminated (at autopsy: 1 was normal, 2 had hydrocephalus and for 1 the parents refused autopsy). Eight fetuses that were delivered had congenital malformations; 3 of them died during the early neonatal period. In 6 of the 8 fetuses with malformations, karyotypes were available and 3 had chromosomal aberrations (trisomy 18, 45XO, and triploidy 69XXX). Spontaneous in utero resolution of the MVM occurred in 10/30 (33.3%) of the cases. Of the 26 infants that remained in follow-up, 16 (61.1%) were normal at 1 month and at 2 years of age. CONCLUSIONS Our data confirm those of previous reports as to the characteristics and outcome of MVM. In the setting of mild fetal ventriculomegaly with a normal karyotype and an absence of malformations, the outcome appears to be favorable.