The aim of the present study was to test the efficacy of the topically active cholinoceptor antagonist, ipratropium, in the treatment of rhinorrhea in perennial nonallergic rhinitis, with special reference to identification of subgroups of responders and increased efficacy from high-dose therapy. Thirty-six adult patients with watery rhinorrhea as a dominant symptom completed the study, which consisted of a 2-week run-in period followed by two 3-week treatment periods with placebo and ipratropium in an ordinary dosage (80 micrograms four times a day) in a double-blind, crossover design, and, finally, an open 2-week period with high-dose therapy (400 micrograms four times a day). The number of nose blowings was 47% lower during treatment with ipratropium in the ordinary dosage than during the placebo period (p less than 0.001). There was an additional reduction during high-dose therapy that was slight but statistically significant (p less than 0.05). Ipratropium had no effect on the number of sneezes or on nasal blockage index. During ordinary-dose therapy, side effects were slight and confined to the nose, whereas the high-dose therapy caused unpleasant nasal dryness and, in a few cases, systemic side effects. It was not possible to separate responders from nonresponders by case history, physical examination, or nasal methacholine testing. It is concluded that intranasal ipratropium is effective in the treatment of watery rhinorrhea in perennial nonallergic rhinitis and that 320 micrograms a day is sufficient in most patients.