Eighty five Chinese patients with diffuse or localized bronchiectasis (non-cystic fibrosis) were studied regarding the prevalence of asthma. Twenty three of the 85 had concomitant asthma, diagnosed by history and reversibility on lung function testing either spontaneously or after bronchodilator. None fulfilled the diagnostic criteria of allergic bronchopulmonary aspergillosis (ABPA). Asthma preceded the onset of bronchiectasis in 13 patients and developed after long duration of bronchiectasis in seven, while the temporal onset could not be differentiated in three patients. Patients with both asthma and bronchiectasis had inferior spirometric values, higher prevalence of bronchial hyperresponsiveness to methacholine, higher prevalence of skin atopy, elevated serum immunoglobulin E (IgE), and more sputum eosinophilia, compared with their non-asthmatic counterparts. Possible mechanisms by which asthma and bronchiectasis predispose to each other include asthmatic obstruction contributing to development of bronchiectasis, and sensitization of airways with increased lability due to microbial colonization of the ectatic bronchial tree.