A 57-year-old woman believed that ibuprofen, prescribed for back pain, improved her idiopathic chronic cough that had been resistant to inhaled and oral corticosteroids. To confirm this observation, we performed an n-of-1 clinical trial with four treatment periods, each separated by a 4-day washout. Ibuprofen 1800 mg/day for 6 days or placebo was randomly allocated in a double-blind fashion with a block size of 4. The number of coughs during the first 30 minutes after awakening were counted daily throughout the study using a tape recorder. Sixty-two coughs/hour occurred while taking ibuprofen, compared with 164 with placebo. We conclude that ibuprofen may be effective in idiopathic chronic cough, and suggest that prostaglandins may be pathogenic factors in some patients.