This paper documents how the frequency of price changes differs across sectors in Korea and what implications such heterogeneity may have for monetary policy. Under heterogeneity, i) monetary policy has larger and more persistent real effects, ii) stabilizing an alternative (optimal) price index that places disproportionately larger weights on “sticky”sectors rather than the consumer price index is welfare improving, iii) the central bank,targeting such an alternative index, should move nominal interest rates slowly, which may justify “gradualism” in monetary policy, and iv) the condition for equilibrium determinacy is different. The results suggest that the monetary authority must consider how firms’ pricing behaviors differ across sectors in the design of monetary policy.