A variety of operational definitions of brand loyalty have been proposed in the marketing literature, and the advent of scanner panel data has further accelerated this trend. This paper surveys the measurement methods of brand loyalty found in prior literature, empirically derives the latent dimensions underlying the various definitions, and validates the reliability and validity of these dimensions by utilizing scanner data. The analysis of the 15 brand loyalty definitions selected for this study revealed that four distinct dimensions are embedded within them, and within the framework of a choice model, each brand loyalty dimension was found to have a different effect on product choice. Based on these results, implications for the utilization of loyalty variables in scanner panel research are presented.