Adenosine monophosphate (AMP) challenge is a diagnostic tool for asthma. The aim of this study is to evaluate the effect of low dose inhaled budesonide (IB) on PC20AMP levels. Seventeen stable mild asthmatic patients were prospectively recruited. After initial testing, patients were administered 400 g of inhaled budesonide. AMP challenge was then repeated at the 12th hour and 5th,15th, 30th, and 90th days of the treatment. AMP challenge resulted in negative in 47% of the patients at 12-hour testing. This study suggests that low-dose IB may return airway responsiveness as early as 12 hours and AMP challenge may be effectively used for treatment monitorization.