We have investigated the effects of inhaled budesonide on the bronchial responsiveness to both directly and indirectly acting spasmogens in man. Following treatment with budesonide or placebo for three weeks in a double-blind, crossover trial with a three-week washout, the response to histamine and bradykinin was determined in ten patients with mild asthma. After treatment with budesonide, the response to both inhaled histamine and bradykinin was decreased when compared with placebo. The PD35 histamine was increased by 1.95 doubling doses and PD35 bradykinin by 2.1 doubling doses. Daily (PEF) recordings were significantly increased during budesonide therapy, the morning PEF by 34.8 +/- 14.1 L/min and evening by 50.3 +/- 23.1 L/min. Baseline laboratory lung function on the study days was not altered by budesonide nor were symptom records altered significantly. Inhaled budesonide therefore inhibits to the same extent the exaggerated response to both directly acting histamine and bradykinin which acts through airway nerves.