We have assessed the effects of terfenadine on rhinitis symptoms associated with the common cold in 91 patients in a double-blind placebo-controlled study. The patients received three doses of either terfenadine 60 mg (n = 44) or placebo (n = 47) at about 12-h intervals, starting in most patients within 48 h from the onset of symptoms. Because of deviations from the protocol, 28 cases were classified as not eligible for efficacy evaluation, but were nevertheless analysed. Excellent/good or moderate efficacy was reported by 63% of eligible and 59% of all patients who received terfenadine (placebo 40% and 51% respectively, p = 0.049 and 0.113 respectively). 68% of eligible and 52% of all patients indicated that they would take terfenadine again (placebo 23%, for both p = 0.002). Two h after tablet intake mean nasal airflow was increased by 11 l.min-1, SD 8 (placebo -1 l.min-1, SD 6, p = 0.005). Symptoms were improved and rhinoscopy showed reduced swelling and redness of the mucosa and reduced nasal secretion and obstruction (basically unchanged in the placebo group). Therefore, terfenadine seems to act favourably on the acute rhinitis symptoms associated with the common cold. Since terfenadine is devoid of anticholinergic activity, nose symptoms during the initial stage of the common cold may be mediated to an important degree by histamine.