Clinical course of one asthma patient (64 years old, female), who had an increased proportion of neutrophils in bronchoalveolar lavage (BAL) fluid, was observed in relation to the proportion of BAL cells and ventilatory function. The patient had large asthma attacks two times during her clinical course for 15 months observed. 1. An increased proportion of BAL neutrophils and suppression of ventilatory function were found after her first large asthma attacks. The increased proportion of BAL neutrophils continued for more than 5 months. A reduction in the proportion of BAL neutrophils was found 3 months after her second large asthma attack, accompanied by improvement of clinical symptoms and ventilatory function. The numbers of total cells and neutrophils in BAL fluid were also reduced. Transient increase in number of BAL lymphocytes was found 13 months after the first large attack when the number of BAL neutrophils was markedly decreased. The number of BAL eosinophils did not change during her clinical course.