Our aim is to identify causal variants for the IL1RL1 gene previously associated with asthma and related phenotypes as well as perform functional assays to uncover the mechanism underlying its involvement in the disease pathogenesis. IL1RL1 has been shown to be sufficient to induce experimental allergic airway inflammation using transgenic and knockdown mouse models. Its expression has been shown to increase in murine and human asthmatic lungs; the ligand for IL1RL1 is Interleukin-33 (IL33). The signaling cascade resulting from the binding of TSLP and IL33 is crucial in eosinophilic inflammation characteristic of asthma. The IL1RL1 gene lies in chromosome 2 in the midst of a cytokine gene cluster with IL1R1, IL1RL2, IL18R1 and IL18RAP: all encoding for proteins involved in the immune response characteristic of asthma. The region is in relatively high linkage disequilibrium, thus an excellent candidate for narrowing down the asthma association signal to one or more causal SNPs.