In this paper we describe the reduction of O-2 and CO2, when both molecules are always present and the balance gas is N-2, at unshielded gold microdisc electrodes in dimethyl sulphoxide (DMSO) in a standard reaction cell. We show that both gases can be reduced in the presence of each other, in the range 3-15 vol.% CO2 and 10-30 vol.% O-2, with minimal cross-interference from "feedforward" and "feedback" reaction products from the individual O-2 and CO2 reduction processes. Well-separated O-2 and CO2 reduction processes were obtained with gold microdisc electrodes when the polarizing voltage was swept typically at 0.1-0.5 V s(-1), and steady state limiting currents were measured which were proportional to the O-2 and CO2 concentrations.