This paper is aimed at validating a detailed reaction mechanism for the formation of the first aromatic rings (benzene and phenyl radical) in a rich premixed acetylene-oxygen-argon flame. Validation has been carried out by confrontation of computed mole fraction profiles of stable and labile species against experimental results. With only specific changes in kinetic data of a few reactions a good agreement was obtained for the mole fraction profiles of C4species. Distinction between singlet and triplet methylene radical was a more profound change brought to the mechanism and needed to obtain a good modelling of C3H3. These changes result in a marked improvement in the modelling of C4H2, C4H3, C4H4, C4H5, C3H3, C3H4and C6H6, accompanied by a better coherence of the mechanism with recent kinetic data measurements. Pathways analyses of bemiene formation show that acetylene addition to C4H5takes place close to the burner and is rapidly superseded by addition of propargyl radicals to allene.