Objective : This study is directed to analyze clinical outcome of fetuses that showed mild ventriculomegaly on prenatal sonography, thus aiding prenatal care, consultation, and further management of such patients. Method : All prenatal sonographic findings from 1996 to 1999 were evaluated. Mild ventriculomegaly of 10-15mm were observed in 60 cases, but only 31 that received continuous prenatal care and underwent delivery in our hospital were studied, whose cases were divided into two groups. The 1st group showed isolated mild ventriculomegaly(IMV, n=21). The 2nd group had mild ventriculomegaly with associated other anomalies(AMV, n=10). Prenatal sonographic findings and medical records of each group were compared and analayzed. Results : In each group(IMV : AMV), the mean maternal age(years; mean±S.D.) was 30.2±3.3 : 28.5±2.5(p=0.139), the gestational age at diagnosis(weeks; mean±S.D.) 27.8±4.3 : 28.3±5.3(p=0.784) and the cephalic index(mean±S.D.) 74.7±5.0 : 74.2±8.9(p=0.87). No statistically significant differences between the two groups were noted. Male babies predominated in the IMV group(61.9%). And resolution in utero was noted in 13 out of those cases. In the IMV group, those with mild ventriculomegaly≥12mm more frequently accompanied delayed development after birth(2/5) than those〈12mm(1/16). Mild ventriculomegalies≥12mm were more frequent in the AMV(8/10) than in the IMV(5/21), of which finding was statistically significant(p=0.003). Conclusion : Fetuses with mild ventriculomegaly≥12mm on prenatal sonography could be predicted to have relatively high risk of delayed development after birth and associated anomalies. Detailed ultrasonography is necessary to determine the presence of other anomalies in cases with mild ventriculomgaly. If isolated, periodic ultrasonography and consultation are requested. Thereafter, More cases with longer periods of follow-up should be evaluated.