Methane is shown to react with ethene over In-loaded ZSM-5 to higher hydrocarbons such as propene and toluene at around 673 K. Such methane conversion is not catalyzed by proton-exchanged ZSM-5 (H-ZSM-5) under the same conditions, only C2H4 being converted to higher hydrocarbons. By using C-13-labeled methane ((CH4)-C-13) as a reactant, the reaction paths for the formation of propene, benzene and toluene were examined. C-13-labeled propene ((CC2H6)-C-13) is formed by the reaction of (CH4)-C-13 with C2H4. The lack of C-13-labeled benzene revealed that propene is not transformed to benzene, which instead originates entirely from C2H4. The C-13 atom is inserted both into the methyl group and benzene ring in the toluene formed. This indicates that toluene is formed by two reaction paths; the reaction of (CC2H6)-C-13 with butenes formed by the dimerization of C2H4 and the reaction of benzene with (CH4)-C-13. The existence of the latter path was proved by the direct reaction of (CH4)-C-13 with benzene. The reaction of methane with benzene was also carried out in a continuous flow system over In-loaded ZSM-5. The reaction afforded 7.6% and 0.9% yields of toluene and xylenes, respectively, at 623 K.