To determine the pattern of bronchiectasis in hypogammaglobulinaemia we reviewed the CT scans of 38 hypogammaglobulinaemic patients. Twenty-two had bronchiectasis, seven had bronchial wall thickening without bronchiectasis and the remaining nine were normal. The middle lobe was the most common site of bronchiectatic involvement, followed by the lower lobes and the lingula. There were no cases of isolated upper lobe involvement. In patients who had bronchial wall thickening without bronchiectasis the middle lobe and lower lobes were again most commonly affected. It is postulated that in these hypogammaglobulinaemic patients bronchial wall thickening represents a stage of bronchial inflammation prior to the development of bronchiectasis. Patients with X-linked agammaglobulinaemia (XLA) develop bronchiectasis at a significantly earlier age than those with 'common variable' hypogammaglobulinaemia (CVH) (P = 0.02). No correlation was found between the serum levels of immunoglobulin classes at diagnosis and the subsequent development of bronchiectasis.