The purpose of this study was to investigate whether cyclosporine treatment could modify airway responses, thus playing a role in bronchial hyperresponsiveness observed in patients after lung transplantation. We have studied the effect of cyclosporine treatment in rats on subsequent bronchial responses to electrical field stimulation, to exogeneous 5-hydroxytryptamine, and acetylcholine in organ baths. The isometric force of contraction of bronchial smooth muscle was measured. Voltage and frequency responses produced by electrical field stimulation were similar in control and in rat bronchi treated with cyclosporine. Concentration-response curves to exogeneous acetylcholine were superimposed for both groups of animals, as were those to 5-hydroxytryptamine. Our results show that cyclosporine treatment does not affect bronchial smooth muscle contraction and rule out possible contribution of cyclosporine to the bronchial hyperresponsiveness described after lung transplantation.