Abstract A 48-year old man who had been treated with prednisolone, aminophylline, and pranlukast, a leukotriene-receptor antagonist, was diagnosed with Churg-Strauss syndrome based on the findings of asthma, eosinophilia, mononeuropathy, and extravascular eosinophils. Intractable neuropathic pain of the legs was successfully controlled with an N-methyl-d-aspartate receptor antagonist, dextromethorphan. We suggest that dextromethorphan receptor antagonists may be a useful treatment for the pain of neuropathy caused by vasculitis syndrome.