Serum IgE concentration was determined in 17 newborn and 171 children with ages between 1 and 12 months. In the first group, blood was taken from the umbilical cord, and in the second, we used a periferic blood sample. The selection implied the exclusion of children with any suspicion of atopic disease, family history of atopy and recent viral infection. The serum IgE concentration was determined by enzyme linked immunoabsorbent assay (PRIST). The sex, race ( white and non white) and age were analyzed in the children studied. During a follow-up period (24 months) seven children (3,7%) developed atopic symptoms. The serum IgE concentration of the groups studied was higher than in other studies. The mean IgE in each group was as follows : newborns = 0.24 IU/ml; 1-3 months = 1.57 IU/ml; 4-6 months = 7.72 IU/ml; 7-9 months 12.07 IU/ml; 10-12 months = 12.14 IU/ml.