Cysteinyl leukotrienes (Cys-LTs) are potent proinflammatory mediators derived from arachidonic acid through the 5-lypoxigenase (5-LO) pathway. They exert important pharmacological effects by interaction with at least two different receptors: Cys-LT(1) and Cys-LT(2). By competitive binding to the Cys-LT(1) receptor, leukotriene receptor antagonist drugs such as montelukast, zafirlukast, and pranlukast, block the effects of Cys-LTs and alleviate the symptoms of many chronic diseases, especially bronchial asthma and allergic rhinitis. Evidence obtained by randomized clinical trials as also by direct experience derived from patients suffering from asthma and allergic rhinitis justifies a broader role for leukotrienes receptor antagonists (LTRAs). Recently published studies and case reports have demonstrated beneficial effects of LTRAs on other diseases commonly associated with asthma (exercise induced asthma, rhinitis, chronic obstructive pulmonary disease, interstitial lung disease, chronic urticaria, atopic dermatitis, allergic fungal disease, nasal polyposis, and paranasal sinus disease) as well as other diseases not connected to asthma (migraine, respiratory syncytial virus postbronchiolitis, systemic mastocytosis, cystic fibrosis, pancreatitis, vulvovaginal candidiasis, cancer, atherosclerosis, eosinophils cystitis, otitis media, capsular contracture, and eosinophilic gastrointestinal disorders). The aim of this review is to show the most recent applications and effectiveness in clinical practice of the LTRAs.