Patients with primary immunodeficiencies often have symptoms of their disease for months or years before diagnosis and treatment. This is partly because these disorders are relatively uncommon and the infections typical of immunodeficienciey, for example otitis, sinusitis, and pneumonia, are common. We report a case of agammaglobulinemia in an 8-year-old boy with recurrent and severe infection. He was first seen in our hospital for bacterial meningitis in 2006. His immune status revealed panhypogammaglobulinemia and deficiency in mature B lymphocyte. His elder brother also showed deficiency in mature B lymphocyte but mild hypogammaglobulinemia. Some X-linked agammaglobulinemia (XLA) cases may remain undiagnosed because they only show mild hypogammaglobulinemia and they lack repeated infections in childhood.