Selective immunoglobulin A deficiency (SIgAD) is the most common predominantly antibody deficiency, with a wide range of presentations from asymptomatic to severe manifestations. Although many studies have investigated different aspects of SIgAD, no study has yet presented a comprehensive classification of this disease. Based on clinical manifestation of patients and various immune abnormalities associated with SIgAD, this group of patients could be classified into five different phenotypes including asymptomatic, minor infectious, allergic, autoimmune and severe phenotypes. This classification aids physicians in identifying patients and in choosing appropriate management and treatment as well as homogenized groups for molecular and genetic studies.