This systematic review of pooled data shows no evidence of benefit of the use of intermittent or continuous montelukast on the number of wheezing episodes, USMA or OCS use for recurrent wheeze in preschool children. However, there may be subgroups of children with preschool wheeze who do respond to montelukast, but there were insufficient data to determine specific phenotypes of responders, apart from one study which did suggest a genotype which was linked with greater response.