Eighty micrograms of the topically active parasympatholytic ipratropium were applied intranasally 4 times a day to 20 adult patients with perennial rhinitis and severe watery rhinorrhoea in a double-blind placebo controlled cross-over trial. There was a significant reduction in nasal hypersecretion during ipratropium treatment. Fourteen patients preferred the ipratropium period, 3 the placebo period and 3 had no preference. There were no adverse systemic or local effects. Ipratropium was effective also in patients resistant to glucocorticoids, sodium cromoglycate and antihistaminics. As the drug works immediately it can also be used before exposure to known provocating factors. It is concluded that continuous use of this new medication is of value in the management of severe rhinorrhoea in patients with perennial rhinitis, and that the occasional use is helpful in subjects with infrequent attacks of nasal hypersecretion.