Glucocorticoids are known to suppress the biological effects of several inflammatory mediators and to reduce the mediator-induced vascular premeability. However the effect of glucocorticoids on the response of the microcirculation to neuropeptide mediators is not established. The present study was done to determine whether neurogenic plasma extravasation can be inhibited by glucocorticoids. Three groups of rats were treated with different doses of dexamethasone for 5 days(0.5-4mg/kg/d.i.p.). The magnitude of plasma extravasation produced by capsaicin was assessed by using Evans blue dye and Monastral blue pigment as intravascular tracers. We found that dexamethasone reduced the magnitude of plasma extravasation produced in the rat nasal mucosa by capsaicin. Significant inhibition could be demonstrated at a dose of dexamethasone as small as 05.mg/kg d.i.p. There was less Evans blue dye concentration in the nasal mucosa of the dexamethasone pretreated group, which could be observed through the fluocrescence microscope. This might suggest that dexamethasone prevents neurogenic plasma extravasation in the rat nasal mucosa.