Applying nonstationary panel data econometric methods, this paper analyzes the major sources and transmission of inflation in the Gulf Cooperation Council (GCC) countries over the 1980-2008 period. We argue that, in GCC countries, money is essentially demand determined, so that the high collinearity between money and aggregate demand indicators such as non-hydrocarbon output is expected and should be dealt with accordingly. Several important results emerge from the analysis. First, the money supply stands out as a significant determinant of inflation both in short-and long-run. Both foreign prices and the nominal effective exchange rate are shown to be more successful in explaining inflation in the long-run than the short-run. The half-life of the speed of adjustment reveals that it takes about 2.9 years for 50% of a shock to the long-run equilibrium to dissipate. An implication of our results is the case it makes for more sovereign monetary policies in GCC countries.JEL Codes: C32, C33, E31, E50, H30