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=CHFCF 2OCHF 2). R Cl+ O 2 −→ R O 2 + Cl − R O 2 + O 2 −→ R O 2 −+ O 2 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.