The value of three objective tests of the nasal mucosa in 22 patients with perennial non-allergic rhinitis treated with a topical corticosteroid has been investigated. Placebo and three different dosages of a new steroid, budesonide, were administered intranasally using a double-blind, cross-over technique. Nasal airway resistance was not reduced by the steroid treatment as compared with the placebo treatment. Eosinophilia in nasal smears was reduced by budesonide. However, the value of this test was decreased by the fact that eosinophilia was found in less than 50% of the patients at the beginning of the trial. Metacholine-induced nasal secretion was significantly reduced by the budesonide treatment. Symptom scores for nasal obstruction, secretion and sneezing attacks were also significantly reduced by the steroid.