The laser Doppler flowmeter is a new instrument that reflects a different physiological parameter other than rhinomanometry for examining the vascular bed of the nasal mucosa. Mucosal blood flow in allergic rhinitis may be an important, but so far little studied, factor. Laser Doppler flowmetry was used to study nasal mucosal microcirculation in seven asymptomatic patients with allergic rhinitis. Topical provocation with birch pollen extract showed a statistically significant dose–dependent increase in blood flow. The method seems useful as an in–vivo model for studying allergic rhinitis.