Bronchoalveolar lavage (BAL) has been studied in asthmatic patients; it is a well-tolerated procedure and can be used in clinical practice to evaluate individual patients. However, the main question is: Does BAL contribute to a better understanding of the pathophysiology of bronchial asthma? The arguments in favour are as follows: (1) experiments in monkeys, indicating that the cells recovered by BAL contribute to the triggering of asthma; (2) demonstration of inflammatory cell (eosinophils, neutrophils, and lymphocytes) influx after allergen inhalation challenge, and (3) in vitro demonstration of cellular activation corresponding with clinical symptoms. BAL offers a new approach to the understanding of asthma. There is a lot of unresolved questions which should encourage us to exploit its potential to the full.