The present study reports the results of an investigation of the effects of an axial electric field (200-8000 V/cm) on the propagation of detonation waves in mixtures of 2CO + O-2 and C2H2 + O-2 + 85%Ar. High speed streak camera and photodiodes were used for detonation velocity measurements. In addition, the voltage across the axial electrodes and the current are monitored as the detonation traverses the electric field region. The present results show that the neither the detonation structure nor its velocity are influenced by the electric field as it traverses the region between electrodes except when a breakdown occurs ahead of the detonation. The breakdown is due to the progressively increasing electric field between the detonation (which acts like a travelling quasi-neutral conducting plasma slug) and the downstream electrode. For a sufficiently strong electric field an arc discharge develops between the detonation and the charged electrode. When a discharge occurs in the unburned mixture ahead of the detonation wave, the mixture is ignited prior to the detonation arrival. This leads to the failure of the detonation since it now propagates into burnt products. Re-initiation of the failed detonation may occur downstream of the discharge section. The present results provide an explanation of the previous observations of Bone et al. [2]. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.