 Cysteinyl leukotrienes CysLTs play an important role in asthma. CysLTs exert most of their bronchoconstrictive and pro-inflammatory effects through activation of the CysLT1-r. As allergic rhinitis appears to be a predisposing factor in the development of asthma and as CysLT-receptors seem to be implicated in the first steps of asthma manifestations, we think it would be of interest to determine if the CysLT1-r is a key mediator in the progression from allergic rhinitis to asthma. We believe it would be interesting to study the expression of the CysLT1-r 