Scanning electrochemical microscopy was used to characterize air bubble/electrolyte interfaces for bubbles of diameter in the millimeter range. Contrary to rigid insulated substrate/liquid interfaces, the approach of the tip of the microelectrode was shown to lead to a deformation of the bubble surface, which was attributed to repulsive forces between the interface and the tip. The deformation amplitude, which could be estimated from the approaching curve, depends on both the total electrode-tip size and interface-tip distance. It was also shown that imaging a bubble in a constant-height mode could be performed despite bubble deformation. (C) 2003 The Electrochemical Society.