Aim of the study was to evaluate correlation between valine and glycine, representatives of essential and nonessential amino acids, in fetuses appropriate and small for gestational age with congenital cytomegalovirus infection. Umbilical venous cord blood was obtained by cordocentesis at 22 to 29 weeks' gestation from 18 women (11 in appropriate for gestational age--A, and seven in small for gestational age--B) fetuses with CMV infection. Plasma amino acids were measured with an Beckman M 121 amino acid analyzer. Maternal valine level was 136.0 mmol/l; fetal valine in AGA and SGA fetuses: 219 and 189 mmol/l respectively. Fetomaternal valine ratio was significantly lower in SGA group (1.39 mmol/l-SGA, 1.61 mmol/l AGA, t = -6.9, p < 0.001). Glycine level in maternal blood was 139.0 mmol/l; fetal in SGA and AGA fetuses 137 mmol/l and 176 mmol/l, respectively. Fetomaternal glycine ratio was also significantly lower in SGA group than in AGA, 1.01 and 1.27 respectively (t = -2.96, p < 0.001). Valine/Glycine maternal and fetal ratio did not show any difference between groups. In congenitally CMV infected fetuses with intrauterine growth retardation there is a decreased valine and glycine level, compared to the congenitally CMV infected fetuses with normal intrauterine growth. There is a lower fetal concentration of these amino acids compared to the maternal level in SGA fetuses. A decreased glycine level compared to the valine level has also been found in congenitally CMV infected fetuses with intrauterine growth retardation.