The records of 240 patients with common variable immunodeficiency, seven with thymoma-associated hypogammaglobulinaemia and 44 patients with X-linked agammaglobulinaemia seen at this centre over the past 20 years, were reviewed. Although substantial advances have been made in treatment there continues to be a delay in diagnosis, as well as high mortality and morbidity rates. Hypogammaglobulinaemia is associated with a high incidence of chronic sinopulmonary infection, chronic diarrhoea, malignancy, joint disease and hepatitis. There is particular concern that infection with mycoplasmas and enteroviruses can be resistant to treatment. The high incidence of lymphoma and gastric carcinoma in patients with common variable immunodeficiency is highlighted.