In this paper, we compare a quantitative cell-based assay measuring the intracellular Ca2+ response to the agonist uridine 5'-triphosphate in Chinese hamster ovary cells, in both microfluidic and microtiter formats. The study demonstrates that, under appropriate hydrodynamic conditions, there is an excellent agreement between traditional well-plate assays and those obtained on-chip for both suspended immobilized cells and cultured adherent cells. We also demonstrate that the on-chip assay, using adherent cells, provides the possibility of faster screening protocols with the potential for resolving subcellular information about local Ca2+ flux.