A number of studies have demonstrated that perturbed cellular calcium homeostasis has been implicated in apoptosis. Some studies showed that selenium compounds were able to induce cell apoptosis. The main objective of this study is to evaluate effect of Na2SeO3 on intracellular Ca2+ levels in SW480 human colonic carcinoma cells. When SW480 cells were exposed to 25 to 100 micrometers ol/L Na2SeO3, we also found that Na2SeO3 was able to induce [Ca2+]i, disruption of mitochondrial membrane potential ((Delta) (psi) m) in SW480 cells by using a confocal laser scanning microscope. Ca2+ channel inhibitor CoCl2 and an intracellular Ca2+ chelator BAPTA completely inhibited [Ca2+]i increase. CoCl2, BAPTA and ruthenium red also inhibited disruption of (Delta) (psi) m. The results suggest that Na2SeO3 is able to increase [Ca2+]i mitochondria permeability transition and Ca2+ is from extracellular Ca2+.