This paper studies how the stock market reacts to zero or small positive sales surprise.Using data from firms listed in the U.S.,the paper shows that before 2003 investors react more to positive earnings surprises while after 2003 they react more to the opposite.When sales forecasts are first reported,investors believe in sales numbers and favor firms that meet or beat sales forecasts,but after 2003,investors grow skeptical,realize the possibility of sales management and trust more in negative sales surprises.One thing in common for both two samples is that Sales Response Coefficients of extreme sales surprises are smaller than those of moderate sales surprises.