In all asthma guidelines, preventive anti-inflammatory treatment is essential in all patients with persistent asthma. Inhaled corticosteroids are the mainstay of treatment in the control of asthma, but other treatments may be used as a monotherapy in patients with mild asthma or as an add-on treatment in those with moderate-to-severe asthma. Leukotriene modifiers are the only validated preventive treatment for all age groups. This review discusses the place of montelukast, a leukotriene receptor antagonist, using guidelines and consensus reports on asthma and rhinitis: the US National Asthma Education and Prevention Program (NAEPP); the British Guideline on the Management of Asthma; the Global Initiative on Asthma (GINA); and Allergic Rhinitis and its Impact on Asthma (ARIA). This review includes new studies that have not yet been considered in guidelines.