Effect of prednisolone on isolated preparations of trachea of normal rats and rats with fibrosing alveolitis was studied. Prednisolone at a concentration of 0.4 microg/l decreased responses of smooth muscle on stimulation of preganglionar nerve fibers at trachea areas with intramural ganglia in rats with acute alveolitis by 48%, while in normal rats--by 19% of control. In trachea preparations without ganglia, prednisolone at a dose of 10 microg/l decreased responses of muscle to the nerve fiber stimulation by 21.3%. The higher prednisolone doses were less efficient: 0.1-10 microg/l glucocorticoid practically did not affect the smooth muscle responses produced by stimulation of muscle cells. In rats with fibrosing alveolitis, 10 microg/l prednisolone restored the smooth muscle responses to control values in preparations of trachea with intramural ganglia. After the prednisolone treatment, amplitude of the rat trachea muscle contraction in response to the nerve fiber electric stimulation did not differ statistically significantly from control and 0.1-10 microg/l prednisolone did not change the response value. The conclusion is made that prednisolone affected the diseased rats more efficiently than the healthy animals. The character of the glucocorticoid effect depends on the presence of intramural ganglia in the trachea wall.