Objectives: To evaluate the value of the ratio of middle cerebral artery pulsatility index (MCA PI) to the umbilical artery pulsatility index (UA PI) for predicting of adverse perinatal outcome in the fetuses with intrauterine growth restriction (IUGR). Methods: A prospective study was performed on 80 pregnant women in Thammasat University Hospital from January to December 2009. The study population comprised 38 pregnant women who delivered IUGR fetuses and 42 pregnant women whose fetuses were normal growth. The MCA PI, UA PI andMCA PI/ UA PI ratio were assessed. Mild IUGR and severe IUGR were defined as a fetus having the fetal weight below the 10th and 5th percentile for the gestational age at birth, respectively. Abnormal MCA PI/ UA PI was defined as the ratio <1.08. Results: Of the 80 pregnant women in the study, the mean maternal age of IUGR fetuses were significantly lower than in normal growth fetuses; 25.53 ± 6.23 years and 32.67 ± 4.90, respectively (P < 0.05). 8 out of 38 women with fetal growth restriction showed abnormal MCA PI/ UA PI ratio (<1.08). Among these, mild and severe IUGR with abnormal MCA PI/ UA PI ratio were 6/30 (20%) and 2/8 (25%), respectively which was demonstrated the significantly difference (P = 0.007). Conclusions: TheMCA PI/ UA PI ratio could be used as the predictor of the fetuses with growth restriction in a particularly severe case of IUGR.