Today, medicinal treatment of asthma over the long term is well codified and involves inhaled corticosteroid therapy, in association or not with beta 2-mimetic substances. Numerous studies have demonstrated the importance of leukotrienes in bronchoconstriction and in the delayed inflammatory reaction of asthma. At the same time, antileukotriene molecules are being introduced. Several are sold in different countries. At present, only one product is available in France: Montelukast. It is officially indicated as a complementary treatment of mild to moderate persistent asthma, not sufficiently balanced by inhaled corticosteroid therapy and as a treatment of exercise-induced asthma. In the future, studies should further define the position of these substances in the long term treatment of asthma.