Triggering factors of hepatic apoptosis can be roughly classified into three groups. Extrinsic causative factors indicate that triggering factors are from external environment or they are foreign to the body such as viruses, alcohol, and drugs. Intrinsic factors include the causative factors that are derived from the liver itself, for example, toxic bile acids and free fatty acids. Immune factors can be either an independent etiological factor or interactive factor during pathogenesis of liver injury. For example, viral infection can uncover internal antigen to expose immune system and further exacerbate the severity of liver injury.