Churg-Strauss syndrome (CSS) is a disseminated small vessel vasculitis characterized by late-onset asthma, upper airways disease, eosinophilia and late neurological manifestations such as peripheral neuropathy. Recently, several cases of CSS have been reported in patients treated with leukotriene antagonists after weaning corticosteroids. We describe a case of CSS developed while the patient was receiving montelukast for asthma treatment, after corticosteroids withdrawal. A causal relationship between montelukast therapy and CSS is hypothesized.