Astemizole, a new oral long acting antihistamine devoid of significant central, sedative or anticholinergic effects, was studied in nine patients with exercise-induced asthma. Most patients received some protection with the active drug after 1 week of treatment (10 mg daily) and all showed less of a fall in FEV1 on exercise 1 week after stopping the drug compared with an initial placebo period (P less than 0.01). A significant reduction in histamine-induced skin reaction (weal size) was also demonstrated (P less than 0.01).