The intervention protocol, which involves testing the effect on bronchial obstruction of pharmacologically modifying the nasal response to environmental antigen, has entered 11 of the projected 12 volunteers and is scheduled for completion within a month. We have shown that airway hyperresponsiveness is a major risk factor for asthmatic response, but has also shown for the first time that a person without bronchial hyperresponsiveness will develop acute asthma to airborne antigen.