This study is a controlled, randomized, and double-blind clinical trial that was performed on 60 patients with renal failure aging over 16 and after three months of hemodialysis. All of the patients have been taken testimonial for both N-acetylcystein and placebo provided that, they do not know which group of study (experimental or control) they will be entered. Patients participating in this study, randomly select a numbered card in sealed envelopes in order to enter the control or the experimental group. Giving the medication and randomization process are done by someone who do not intervene in the experiment, accordingly, this study is double-blind. At the beginning of the study, total serum Malondialdehyde is measured as a basis and prior to the prescription of medication or placebo in both groups. Measurement of this marker is done through spectrophotometry method with malondialdehyde kit from merck company of Germany. Then the main group is given 600 mg of N-acetylcysteine twice daily (within 12 hours) for 6 weeks to be taken before meals. To Control the Correct use of medicines, pills and (placebos) are given to patients every week and at the weekend the empty blisters of pills are collected and counted. If a patient did not consume more than 20% of tablets, he would be excluded. The control group is given placebo tablets similar to N-acetylcysteine (2 times a day) within 12 hours in 6 weeks. Placebo was similar to that of N-acetylcysteine tablets in terms of shape, colour and flavour. Its components include: micro-crystalline, cellulose, lactose, corn starch, sorbitol and talc (2% of the total tablet weight). Upon completion of the study period (6 weeks), serum Malondialdehyde, in two groups are measured again using the above mentioned method. Finally, the collected data will be analyzed.