Cigarette smoking during pregnancy has been incriminated for several adverse effects on the fetus, such as intrauterine growth retardation (IUGR), fetoplacental circulatory abnormalities and hypoxia. α-Fetoprotein(α-FP) is mainly synthesized in the fetal liver. The concentrations ofα-FP and erythropoietin (EPO) were measured in the cord blood of 55 fullterm newborns whose mothers smoked ≥5 cigarettes per day and in 44 fullterm newborns of nonsmoking mothers. The mean birth weight (BW) ± SD of the neonates of the mothers who smoked and did not smoke during pregnancy was 3.05±0.40 kg and 3.37±0.45 kg (p=0.003), respectively. The α-FP concentrations in the newborns of the smoking and the nonsmoking mothers were 118±114 and 63±47 ng/ml, respectively (p=0.001). The EPO concentrations were 57±68 and 32±22, respectively (p=0.025). A significant positive correlation was found between the number of cigarettes smoked per day and both the EPO(r=0.322, p<0.01) and the α-FP (r=0.417, p<0.001) concentrations. There was a significant negative correlation between the α-FP concentrations and the BW (r=-0.210,p< 0.05), whereas there was no significant correlation between EPO and BW (r=-0.166, p>0.1). The findings indicate that the IUGR observed in neonates of smoking mothers is not related to fetal hypoxia, but both the increased α-FP concentrations and the growth failure result from a direct toxic effect of the tobacco smoke on the fetal tissues. Also, the effect of cigarette smoking on the amniotic fluidα-FP concentrations, frequently used for the prenatal diagnosis of genetic disorders, should be investigated.