Background:Diabetes mellitus is the leading cause of CKD. Oxidative stress is increasing during the course of DM.Objective:To study the preventive role of oral N-acetylcysteine on the proteinuria in type II diabetic patients.Methods:The study was conducted on 40 diabetic (type II) and hypertensive patients with normal serum creatinine and absence of proteinuria or microalbuminuria, used 600 mg of NAC twice daily for 9 months in moderate doses of. The control group was 30 diabetic (type II) and hypertensive patients with normal serum creatinine and absence of proteinuria or microalbuminuria.Results:When we compare Albumin/creatinine ratio between patients and control groups, we found no significant difference between both groups at the end of the study. (P value: 0.598). There was also, no significant difference in prorein/creatinine ratio when we compare between both groups at the end of the study. (P value: 0.826).Conclusion:No significant effect on the prevention of proteinuria in diabetic and hypertensive patients by using oral N-acetylcysteine for 9 months.