A fluorimetric method for the study of intracellular Ca++ metabolism in rat pancreatic acini is described. Following previous reports on the utilization of the new intracellularly trapped fluorescent dye fura2 in human lymphocytes, the authors point out the relevance of the cellular and fura2 concentration as critical issues for an accurate evaluation of Ca++ homeostasis. A dose-response curve to both carbamoylcholine and cholecystokinin is reported, demonstrating the ability of the cells to respond to hormonal stimulation with a transient Ca++ peak. The almost complete absence of noise in the recorded traces allow to carry out an evaluation of the intracellular mechanism related to Ca++ mobilization with a very high sensitivity.