Microwave discharges in a flow system containing hydrogen-carbon monoxide-argon mixtures have been sampled by a time-of-flight mass spectrometer. Depending upon experimental conditions, from 5 to 30 percent of the carbon monoxide was converted to methane, acetylene, and carbon dioxide. The formation of the major gaseous products was studied as a function of reactant gas composition, pressure, microwave power, and flow rate. The consumption of carbon monoxide appears to be first order at short residence times. Ions were sampled from the discharges at pressures below 5 torr. The most abundant ions were h3o+, hco+, and primarily hydrocarbon ions in the c2, c3, and c4 regions.