In this chapter, we propose an empirical model of the long-run determinants of the inflation rate in WAEMU member countries. Understanding the economic processes that drive inflation is important because prices are an element of the competitiveness of economies. Using an econometric test that allows us to select appropriate macroeconomic variables that induce inflationary pressures, we find that in the WAEMU countries money supply is not the sole determinant of inflation in the long run. Other factors such as supply-side constraints and pass-through effects also play a significant role.