The marine toxin yessotoxin(YTX)and its analogues have been detected in shellfish samples in Chinese coastal areas and they pose a potential threat to public health.Many YTXs toxicity studies have been carried out worldwide,but the process is still indeterminate.In order to study the toxicity of yessotoxin on Hela cells and analyze the possible action mechanism,MTT assay,optical microscope observation,Hoechst 33342 chromatin staining,DNA gel electrophoresis,rhodamine 123 staining,and calciumsensitive laser scanning confocal microscopy were conducted in this paper.The results demonstrated that YTX could induce a significant reduction of Hela cell viability and the cytotoxicity of the toxin was dosedependent.Meanwhile,the usual hallmarks of apoptosis could be detected,including chromatin condensation,DNA laddering,and loss of mitochondrial membrane potential.Furthermore,YTX caused cytosolic calcium levels to increase in Hela cells.The change of intracellular calcium concentration may be the main cause of cell apoptosis induced by YTX.