A catalytic composition is obtained by mixing at least one chromium compound with at least one aryloxy compound of an element M selected from the group formed by magnesium, calcium, strontium and barium, with general formula M(RO)2-nXn, where RO is an aryloxy radical containing 6 to 80 carbon atoms, X is a halogen or a hydrocarbyl radical containing 1 to 30 carbon atoms and n is a whole number that can take values of 0 to 2, and with at least one aluminum compound selected from hydrocarbylaluminum compounds (tris(hydrocarbyl)-aluminum, chlorinated or brominated hydrocarbylaluminum compounds) and aluminoxanes. The catalytic composition can be used in an ethylene oligomerization process, in particular to produce 1-hexene.