Beta cells secrete insulin in response to glucose stimulation, a process that is cytosolic calcium-dependent. During sustained physiological stimulation, beta cells express oscillatory changes in intracellular calcium concentration that spread over a given islet of Langerhans in a wave-like manner. Electrophysiological records from a single cell inside the beta cell syncytium show that the single cell electrical activity is well synchronized with the calcium oscillations indicating tight coupling between calcium and electrical changes. However, network properties of beta cells in vivo remain elusive, mostly because of the inherent limitation of electrophysiological recording with the pipette – namely the “one pipette – one cell” rule. To circumvent this limitation and to assess the properties of the tightly electrically coupled network of beta cells at a systems level, simultaneous recording of a large number of cells is needed, a task most suitable for voltage sensitive dyes. Recently, a new generation of voltage sensitive dyes was reported (1) that utilize photo-induced electron transfer as a voltage-sensing mechanism, providing a more robust response to a voltage change than the previous generations of the voltage sensitive dyes. We used VoltageFluor dye VF2.1.Cl to record oscillatory changes in membrane potential in mouse pancreatic slices using confocal fluorescence imaging. With this method, electrical activity of many (>50) cells could be recorded simultaneously. Glucose responding cells showed a stimulus-dependent depolarization that was followed by a sustained oscillatory behavior. Waves of depolarizations were periodically spreading over the plane of an islet. The wave propagation was similar in its speed as the propagation of calcium waves in pancreas tissue slices during the oscillatory phase reported previously (2). In contrast, the repolarizing phase in the electrical activity seems to be at least partially uncoupled with regard to the calcium activity. The repolarization spreading over the plane of an islet showed different spatio-temporal properties than the depolarization waves. Moreover, the pattern of the propagation of repolarization has not been predictable. To directly determine the relationship between the electrical and calcium waves at higher temporal resolution, we recorded both simultaneously, the calcium oscillations from the plane of islet and potential changes in a beta cell from the network. The former was recorded using OGB-1 using a CCD camera and latter with a patch pipette in whole-cell patch-clamp configuration. Electrical activity was best correlated to the calcium oscillation in the nearest group of cells, relative to the patch pipette.