Congenital Pelger-Huët anomaly is an autosomal dominant disorder affection leukocyte differentiation manifested by the presence of unsegmented of bilobed nuclei with increased condensation, but it is generally assumed that it has no clinical effects. We observed a case of congenital Pelger-Huët anomaly in 9 year-old boy. He was admitted to Ewha Womans University Hospital due to fever and diagnosed as viral infection of upper respiratory tract. On routine peripheral blood examination, we found majority of the neutrophils had uni-or bilobed nuclei. In familial examination, his mother & brother have had Pelger-Huët anomaly without any significant symptoms. On neutrophil function test, moderate defect of chemotaxis was noted.