The effect of N- acetylcysteine on the level of tumor necrosis factor-a (TNF-α) and liver parenchyma injury in an experimental rat model of obstructive jaundice were investigated. Thirty-six Wistar-Albino rats weighing 250- 300 g were randomly divided into three groups of 12 animals in each, as sham-operated, bile duct ligated plus N- acetylcysteine (treatment), bile duct ligated plus saline administered (control). After the operation, the rats in treatment and control groups were administered NAC and saline, respectively. After 10 days of treatment, liver function tests were performed and plasma TNF-a levels were determined in all rats to assess the parenchymal damage. Parenchymal damage and plasma TNF-α level were significantly lower in the treatment group, compared with the control group. N-Acetylcysteine can be useful in decreasing the parenchymal damage in the liver and suppress the plasma TNF-α level in experimental obstructive jaundice.