AbstractRecent studies of the effects of platelet‐activating factor (PAF) on huan and animal airways would support a putative role for this lipid mediator in asthma. PAF can induce many aspects of the clinical and pathological features seen in asthmatic airways such as airway oedema, eosinophil accumulation in the airway wall, and bronchial hyperresponsiveness. PAF has potent activity as a chemotactic agent and as an activator of eosinophils, which are prominent cells in asthmatic airways, through the activation of specific surface receptors. The interaction between PAF and eosinophils may be crucial in the pathogenesis of bronchial hyperresponsiveness in asthma. A role for PAF in asthma can now be studied using the recently developed antagonists of the PAF receptor.