A‘nasal pool’(NP) device, a compressible plastic container with an adapted nozzle, was used to perform a continuous 10-min nasal provocation and lavage. This novel technique brings known concentrations of agents into contact with a large and defined area of the nasal mucosal surface for extended periods of time. Simultaneously, the surface exudations/secretions of the same nasal mucosa are effectively sampled by the NP fluid. A concentration-response study of histamine (80, 400 and 2000 μg/ml) was performed in 12 normal subjects on three different occasions. Exudation of plasma albumin into the lavage fluid was measured to quantitate the histamine-induced airway inflammation. The effect of the dwell time on exudation was examined using histamine (400 μg/ml) instilled in the nasal cavity for time periods from 10 sec to 10 min. The time course of histamine-induced plasma exudation response was studied by exposing the mucosa to histamine (400 μg/ml) for 12 min, with the NP renewed every minute. Allergen-provocations were performed in subjects with hay fever and TAME-esterase activity in the returned lavage fluid was determined to indicate the degree of response. Histamine produced a concentration-dependent increase in albumin levels in the NP fluid; 123·3 ± 25·6, 213·8 ± 19·7 and 430·2 ± 32·0 μg/ml (mean ± s.e.m.), respectively. The time-course study demonstrated that plasma exudation into the lumen occurred promptly and that the exudation response reached a maximum after exposure to histamine for 6–10 min. The dwell-time experiments supported this finding. After 10 min the exudation appeared to decline despite the continued presence of histamine. Allergen provocation resulted in a concentration-dependent increase in TAME-esterase activity of the NP-fluids. It is concluded that the NP technique provides new possibilities in studies of pathophysiology and pharmacology of human airway mucosa. With the NP technique controlled concentrations of mediators, drugs, tracers, etc. can be applied for desirable lengths of time on a well-defined mucosal surface area. This particular area is gently and effectively lavaged during the presence of the NP fluid and when the fluid is recovered by decompressing the NP device.