Immunodeficiency affected by antibody formation is most common among primary immunodeficiencies. Selective IgA deficiency is more common but, one or more IgG subclass level is low or deficient in some patients. Patients with antibody production deficiency are vulnerable to pneumococci, staphylococci and H.influenzae leading to sinusitis, otitis media and pneumonia. A 10-year-old girl had suffered from frequent upper respiratory infections, a history of tuberculous lymphadenitis tuberculosis medication, and frequent pneumonia that requires hospital adimission. Her height and weight were below 3 percentile normal growth as a manifestation of failure to thrive. When she had another severe pneumonia, all the immunologic test was normal at first, and then we checked the IgG subclass levels. Her IgG1 was within normal, IgG2 was very low, IgG3 and IgG4 was not detected. We report a case of IgG subclass deficiency in frequent upper respiratory infection and failure to thrive.