A computerized search was carried out using MEDLINE, Clinical Evidence, Cochrane library, and EMBASE databases to extract trials where the add-on effects of LTRA vs LABA were compared in asthmatics all maintained on a constant dose of inhaled corticosteroid. All authors carried out the search—by checking for suitable trials as evident from the title and abstract—independently of one another. All trials were required to be of a randomized controlled design in which investigators were blinded to treatment, to be ethically approved, and to have results clearly available from the text. Studies were included irrespective of whether they were supported by the pharmaceutical industry. The following key words were used in the search: “asthma,” “long-acting β2-agonist,” “leukotriene receptor antagonist,” “inflammation,” “lung function,” “exacerbations,” “salmeterol,” “formoterol,” “montelukast,” “zafirlukast,” and “pranlukast.” Relevant fully published articles were then selected and the following data extracted: study design, number of patients, length of study, mean inhaled corticosteroid dose, which randomized treatments were used, effects on the primary end point, and effects on FEV1, PEF, symptoms or quality of life, inflammatory biomarkers, AHR, and exacerbations were measured. Following statistical consultation, it was determined that there was too much heterogeneity (in terms of different primary end points, variable time of measurements after dosing, different delivery devices, different LTRA used, and different salmeterol doses) between the trials to proceed to a formal metaanalysis.