Nasal provocation tests with methacholine, histamine, and allergen were performed outside the pollen season in 26 pollen-allergic subjects with the aim of sampling nasal secretions for biochemical characterization. Sugar analyses showed that methacholine-induced secretions were a mixture of serous and mucous glycoproteins. Compared with published sputum values, the levels of proteins and sugars were approximately 5 times lower in the methacholine-induced secretions (protein, 6 mg/ml; hexose, 2 mg/ml), whereas the albumin concentrations were comparable (1 mg/ml). Histamine-induced secretions as well contained a mixture of serous and mucous glycoproteins and a high albumin level (3 mg/ml), indicating a relatively higher degree of transudation than in methacholine- and allergen-induced secretions. Allergen-induced secretions had a low dry weight (mean, 19 mg/g; p less than 0.05) and protein (mean, 4 mg/ml; p less than 0.01) content compared with that in methacholine- and histamine-induced secretions; they contained mainly mucous glycoprotein, and the albumin level was relatively low. Thus, nasal secretions have lower dry weight, sugar and protein content than does sputum; histamine provokes marked transudation; methacholine and allergen do not; methacholine and histamine produce a mixture of serous and mucous glycoproteins; allergen produces mainly mucous glycoproteins.