Airways resistance to electrical field stimulation of the vagus nerves was applied to study the efficacies of atropine and trospium chloride in anesthetized guinea pigs. Stimulation induced an airways resistance that was reproducible, thereby significantly lowering blood pressure and reducing heart rate (p less than 0.05). The induced airways resistance was antagonized using 5 micrograms/kg of either atropine or trospium, but was unaffected by physiological sodium chloride solution. At the dose 10 micrograms/kg, trospium chloride was significantly more potent than atropine which showed only slight augmentation in activity. The present results demonstrate that this procedure can be utilized to investigate, both qualitatively and quantitatively, the actions of anticholinergic and bronchospasmolytic agents in laboratory set-ups.