Many granulites contain high density CO2-rich fluid inclusions; These have played a decisive role in the elaboration of the concept of carbonic metamorphism. It requires that some CO2-rich fluids are present during peak metamorphism, an idea now severely challenged by several workers. For synmeta-morphic inclusions, neither high density nor coincidence between CO2 isochores and mineral P-T estimates are sufficient criteria. Synmetamorphic fluids are identified from three sets of arguments: 1) Earliest primary inclusion densities must be consistent with P-T metamorphic conditions. 2) Later fluids should fall on different isochores (characterization of the post metamorphic P-T trajectory). 3) Fluid composition must be compatible with the metamorphic mineral assemblage.