There are two classes of leukotriene-modifying agents: the 5-lipoxygenase inhibitors and the cys-LT1receptor antagonists. Both of these classes were initially studied in instances of provoked asthma, such as exercise-and aspirin-induced asthma, and have been effective in these cases. With such positive results, there has been great interest in their effectiveness in chronic asthma. Studies using these agents as first-line therapy in chronic asthma have been promising, and work is ongoing to determine how these agents compare with existing therapy and how they can be combined with concomitant medications for asthma.