A rhythmic bioelectrical activity, composed of slow waves and spikes, plays a central role in coordinating contractions in much of the gastrointestinal tract. This chapter addresses the current state of knowledge of the electrical activity contributing to the regulation of GI contractions, with a specific focus on organ-level excitation in the stomach and small intestine. Emphasis is placed on data obtained from extracellular recordings, which effectively profile patterns of bioelectrical propagation over large tissue scales. Recent advances in understanding whole-organ excitation from high-resolution (HR) electrical mapping studies are discussed in particular detail. Lastly, clinical and research questions of current interest are identified.