The objective of the present study was to investigate the cytotoxicity of adriamycin in liver cells (group A), and the protective effect of squalene to the hepatocytes to which adriamycin-induced cytotcxicity (group B) was examined by transmission electron micro-scope. In the group A, The cisternae of rough endoplasmic reitculum and smooth endoplasmic reticulum are dilated/disoriented at 24 hours and 48 hours. The inner and outer membrane of mitochondria are detached or destructed , and attached ribosomes of rough endoplasmic reticulum are diminished in number. The cisternae of the smooth endoplasmic reticulum are dilated, and the cristae of mitochondria are disrupted at 72 hours and 96 hours. In the group B, the cisternae of the rough endoplasmic reticulum and smooth endoplasmic resticulum are dilated at 24 hours. The cisternae of the smooth endoplasmic reticulum are dilated at 48 hours. The cell organelles of hepatocytes are recovered from cytotoxicity at 72 hours. These results suggest that 50 is not only concerned with composition of the membrane system of the cell organelles but also decreased the cytotoxicity of the hepatocytes.