A process is disclosed for converting a hydrocarbon reactant to a product comprising CO and H.sub.2. The process comprises: (A) flowing a reactant composition comprising the hydrocarbon reactant and oxygen or a source of oxygen through a microchannel reactor in contact with a catalyst under reaction conditions to form the product, the microchannel reactor comprising at least one process microchannel with the catalyst positioned within the process microchannel, the hydrocarbon reactant comprising methane, the contact time for the reactant composition within the process microchannel being up to about 500 milliseconds, the temperature of the reactant composition and product within the process microchannel being up to about 1150.degree. C., the conversion of the hydrocarbon reactant to carbon oxide being at least about 50%. The product formed in step (A) may be converted to a product comprising CO.sub.2 and H.sub.2O in a microchannel reactor.