Common variable immunodeficiency (CVI) is a heterogeneous immunodeficiency syndrome characterized by hypogammaglobulinemia, recurrent bacterial infections, and a variety of immunological abnormalities. In addition to recurrent infections, patients with this syndrome also suffer from an increased incidence of autoimmune disease and malignancy. Because the spectrum of associated diseases is broad, patients with CVI are seen by a variety of medical specialists. In this review, the pathogenesis, clinical manifestations, diagnosis, and treatment of CVI are discussed.