Smoking during pregnancy is associated with maternal and fetal complications. In the present study the effect of maternal smoking on neonatal cellular blood components was investigated. The values of whole blood cell count, leukocyte differential count, and thrombocyte and reticulocyte counts were determined and compared in cord blood of neonates of nonsmoking (n = 89) and smoking (n = 53) mothers. The variables of the erythrocyte and thrombocyte count were not different in cord blood of neonates who were exposed to smoke and in those who were not. In the reticulocyte range the reticulocyte count was significantly lower in the smoking group, while the reticulocyte subsets remained stable. The neutrophils were significantly lower in cord blood of neonates of smoking mothers (p < 0.05). The latter finding might be an explanation for the enhanced incidence of postnatal infection seen in children of smoking mothers.