The role of leukotriene receptor antagonists in the treatment of persistent asthma is in evolution. Pivotal 8-12-week, randomized, controlled trials in both adults and children have shown efficacy, as defined by standard asthma outcomes. Tolerance to therapy did not develop, nor did rebound worsening of asthma symptoms once therapy was withdrawn. In a comparator trial of montelukast versus beclomethasone, the average percentage change from baseline in forced expiratory volume in 1 second was greater with the inhaled corticosteroid preparation; however, improvements in other asthma outcomes were similar. There was considerable heterogeneity of pulmonary response with both treatments, with good and poor responders in both groups. In an open-label, crossover comparison of montelukast versus cromolyn, both parents and children preferred montelukast, thus regimen adherence was greater with montelukast. Additional long-term, randomized, controlled trials will define the effectiveness of leukotriene receptor antagonists compared with established controllers, thus determining the leukotriene receptor antagonists' place in asthma management.