Leukotrienes play a major role in the underlying pathophysiology of asthma. Leukotriene-receptor antagonists and direct leukotriene-synthesis inhibitors may be important new agents in maintenance therapy for asthma. Their role may also extend to attenuating exercise-induced and allergen-induced bronchospasm. This article reviews the effectiveness of available leukotriene modifiers in various clinical studies, reviews their adverse effects profile, and discusses their potential roles in the management of asthma.