Leukotrienes have been demonstrated to play an important role as mediators of many pathophysiologic alterations of asthma. Pharmaceutical companies have thus promode many efforts to synthesize new drugs with inhibitory activity on 5-lypoxygenase or with functional antagonism on cystenyl leukotriene receptors. Several compounds have been studied in humans, and some of them should soon be on the market. One of these compounds, ICI 204,219 ("accolate"), a receptor antagonist active by the oral route, has been proven capable of preventing bronchoconstriction induced by several stimuli (allergen, exercise, cold air, etc.) and of improving symptoms and lung function in spontaneous asthma. This effect augments the bronchodilation induced by inhaled beta 2-agonists. On the other hand, no relevant side effects have been reported. However, antiinflammatory properties of this compound must be demonstrated. This new category of antiasthmatic drugs should be recommended for mild-to-moderate asthma, although future studies might demonstrate their efficacy in potentiating or substituting inhaled steroids.