Common variable immunodeficiency (CVID) is the most frequent primary immunodeficiency in adults. It is characterized by severe hypogammaglobulinemia. Males and females are equally affected. The prevalence of the disease in France is probably arround 1/25,000; however CVID is rare in people from Asian ancestry and almost absent in Blacks. The deficit is familial in 20-25% of the cases. Clinical onset is usually during the third decade of life but may also concern children or seniors. Delay for diagnosis often remains of several years. Upper respiratory tract infections are the most frequent complications of CVID (> 85%) and may lead to severe bronchiectasis. Gastrointestinal and liver disease, autoimmune cytopenia, splénomegaly and lymphoproliferative disease may also complicate CVID. A specific genetic defect can be demonstrated in less than 5% of the cases. Therapy relies on IV or SC substitution using polyvalent immunoglobulins.