The effects of terbutaline sulphate were studied in 30 patients who presented with chronic cough at an allergy clinic. After a three week baseline period terbutaline and its placebo were given for two periods of three weeks each in a randomised, double blind, crossover manner. Patients kept a daily record of day and night cough scores and peak expiratory flow readings. Twenty one patients responded to terbutaline; placebo produced no significant effect. Both day and night cough scores (p less than 0.001) and peak expiratory flow rates were significantly improved (p less than 0.05) by the end of the first week of treatment with terbutaline. This improvement was achieved with only a fairly small change in airway calibre.