Background: Diets rich in fruits and vegetables have been linked to reduced rates of several cancers. Pterostilbene, a stilbenoid related to resveratrol, is a potent antioxidant derived from blueberries. We have shown that pterostilbene inhibits pancreatic cancer cell growth in vitro by inducing apoptosis. Apoptotic pathways may involve disruption of mitochondrial membrane integrity. We investigated the effect of pterostilbene on the mitochondrial membrane integrity of two pancreatic cancer cell lines, MIA PaCa-2 and PANC-1.Methods: JC-1 is a cationic dye that exhibits potential-dependent accumulation in cells with healthy mitochondria. This accumulation leads to the formation of red fluorescent aggregates and a fluorescence emission shift from green to red. Mitochondrial depolarization causes JC-1 leakage and decreased mitochondrial dye aggregation. Mitochondrial depolarization is indicated by a decrease in the red / green fluorescence intensity ratio. Pancreatic cancer cells (3 x 105) were cultured using standard techniques. After 24 hours, 1 x 106 cells were loaded with 2 micrograms of JC-1 for 20 minutes. Cells were then treated with pterostilbene or DMSO control for an additional 20 minutes. Cells were trypsinized, resuspended in PBS and evaluated by flow cytometry.Results: MIA PaCa-2 red/green fluorescence intensity ratio changed from 2.45 with DMSO control to 0.18 with 75 micrograms of pterostilbene treatment. Similarly, this ratio decreased in the PANC-1 cell line from 2.03 in DMSO control to 0.41 with the same pterostilbene treatment. Ratios from treated cells were similar to positive CCCP controls, 0.28 and 0.67, in MIA PaCa-2 and PANC-1 respectively. Thus, pancreatic cancer cells show significant mitochondrial depolarization in response to pterostilbene treatment (p<0.02). Conclusions: Herein we have demonstrated for the first time that pterostilbene induces mitochondrial membrane depolarization in pancreatic cancer cells in vitro. This provides an initial mechanism for the previously observed growth inhibition and increased apoptosis when pancreatic cancer cells are treated with pterostilbene. Further in vitro mechanistic studies and in vivo experiments are warranted and planned to determine the potential role for pterostilbene in pancreatic cancer treatment.