Cough is frequently a symptom in bronchial asthma. Appropriate treatment of asthma is usually associated with a reduction in cough. The relationship between cough and bronchoconstriction is outlined and the role of various airway receptors in the genesis of the two responses is discussed. Experimentally, cough and bronchoconstriction may be separated: inhalations of iso-osmolar aerosols of low chloride ion content appear to be selectively tussigenic and do not cause broncho-constriction. Numerous irritants induce cough and broncho-constriction. Topical lignocaine will abolish cough but has no effect on bronchoconstriction. Beta-agonists and anticholinergic drugs will reduce or prevent bronchoconstriction induced by an irritant and may suppress cough. Cough is mediated by airway receptors and it is possible that broncho-dilating agents act as cough suppressors because they "reset" airway receptors.