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Arsenic is a devastating environmental pollutant that has caused severe pollution of ground water in Bangladesh. In this study, Spotted Snakehead (Channa punctatus, Bloch), a common freshwater fish of Bangladesh was exposed to sodium arsenite (NaAsO) to evaluate its toxic effects on that fish. Different 2 concentrations of NaAsO ranging from 0.5 mM-2 mM were used in this investigation. When the fishes were 2 exposed to high concentration (2 mM) of NaAsO, they died within 2 and half hour. However, as the 2 concentrations decreased, the survival period increased gradually. For 1mM and 0.5 mM of NaAsO, the 2 survival time was over 5 hours and 18 hours, respectively. Survival durations of the exposed fishes did not vary according to different water sources such as distilled water, pond water and tap water as used in this study. Trypan blue dye exclusion test revealed that NaAsO reduced liver cell viability in a concentration-dependent 2 manner. 1 mM and 2 mM of NaAsO decreased cell viability to 68% and 38%, respectively. However, 0.5 mM 2 did not show any significant effect. Later, the molecular mechanism of the liver cell death was examined. It was found that the chromosomal DNA of liver cells were fragmented which suggest that NaAsO might induce death 2 of those cells through apoptosis, a process that involve fragmentation of DNA.