Eosinophil count (EC) were obtained from 312 newborns with and 172 without family history of atopy (FHA). The EC were higher in infants with than without FHA. Elevated EC were recorded in babies of parictaria sensitive mothers born in the spring, as compared to other seasons. The predictive value of EC with regard to development of atopic diseases up to 18 months of age was prospectively studied in 103 newborns with FHA. Using 5 × 108 cells/1 as cut-off level the predictive allergy value was 41%. Elevated EC appears to be a marker of atopy in newborns.