The electrochemical reduction of the anaesthetic agent enflurane was investigated at gold disc microelectrodes in the presence of oxygen in DMSO solvent. The superoxide anion radical, formed from the electro-reduction of dissolved oxygen, is shown to react with enflurane, complicating their simultaneous detection. The kinetics of the enflurane/superoxide reaction are found to be first order with respect to both superoxide and enflurane with a rate constant of 0.25 M-1 s(-1) determined by three independent methods: steady-state voltammetry, digital simulation of cyclic voltammetric data and UV-vis spectroscopic analysis. The likely reaction scheme is outlined below (where R = CHFCF2OCHF2). R-Cl + O-2(.-) --> R-O-2 + Cl- R-O-2(.) + O-2(.-) --> R-O-2(-) + O-2 or R-O-2(-) + R-Cl --> R-OO-R + Cl- or R-O-2(.) + R-O-2(.) --> [R-OOOO-R] --> R-OO-R + O-2 The electro-reduction of oxygen in the presence of enflurane is found to be dependent on electrode size and enflurane concentration. Using small electrode sizes, the reduction is shown to be a single one-electron process, since the homogeneous reaction kinetics are effectively 'out-run'. At larger electrode sizes, or with higher concentrations of enflurane, the reduction current is enhanced via the catalytic formation of oxygen, formed from the reaction between superoxide and enflurane.