The production of aromatic compounds directly from methane using catalysts based on zeolite HZSM-5 impregnated with molybdenum was investigated using a flow reactor at 750 degrees C. Main products were benzene and naphthalene as well as toluene and others like azulene in smaller amounts. Naphthalene appeared after benzene following an induction period suggesting a consecutive reaction path. A transient behavior in the production of naphthalene was observed along the time on stream, being benzene practically the only product at the steady state. The transient behavior disappeared when increasing contact time, which produced more naphthalene at the expense of benzene.