An aluminosilicate type catalyst and its use in the aromatization of a C.sub.2 -C.sub.4 light-gas cut in the presence or not of olefins is described.The catalyst is characterized by the following composition expressed by weight:a) 0.01 to 10% by weight of galliumb) 0.1 to 99.49% of a matrixc) 0.5 to 99.99% of a zeolite having the following approximate chemical formula:M.sub.2/n O, Al.sub.2 O.sub.3, xSiO.sub.2whereinM represents a proton and/or a metallic cation,n is the valency of said cation,x is a number ranging from 12 to 1000, said zeolite having a MFI structure being synthesized, moreover, in a fluoride medium and having a fluorine content ranging from 0.02 to 1.5% by weight incorporated during synthesis.