The effect of a daily dose of 400 mug beclomethasone dipropionate aerosol intranasally has been investigated in a double-blind cross-over trial in 29 patients with hay fever. The effect on the nasal symptoms was so pronounced in 25 patients that further symptomatic treatment was unnecessary. Beclomethasone dipropionate aerosol had, on the other hand, no direct effect on itching in the eyes, which is in accordance with the fact that biochemical investigations did not show any sign of suppression of the adrenal function. It is concluded that beclomethasone dipropionate aerosol intranasally is an effective and apparently harmless way of controlling the nasal symptoms in hay fever.