Primarily composed of cells on a porous membrane embedded in microfluidic channels, organ-on-a-Chip (OOC) models are coming into the spotlight as an innovative, new approach to in vitro modeling. However, more work is required to understand the impact OOCs have on cellular function including basal metabolism, barrier resistance and oxygen consumption. Electrochemical sensor-based cellular microphysiometry provides a noninvasive, real-time methodology for monitoring these attribute and can be applied to develop robust, automated assays for organ toxicology, but only few to date have been used with OOCs. In this presentation, we define organ-on-a-chip systems, outline which have been studied with integrated sensors, and present a novel method to study cells cultured directly on a porous membrane.