This article evaluates the performance of the Arab Gulf Cooperation Council (GCC) banking industry in the context of the Structure-Conduct-Performance (SCP) hypothesis in the period 1993 to 2002. This article uses panel estimation differentiating between bank fixed effects and country fixed effects. It examines the Relative-Market-Power (RMP) and the Efficient-Structure (ES) hypotheses differentiating between the two by employing a nonparametric measure of technical efficiency, and finds that the banking industry in the Arab GCC countries is best explained by the mainstream SCP hypothesis. The empirical results do not find any support for the Hicks’ (1935) ‘Quiet Life’ (QL) version of the market power hypothesis.