The primary cause of morbidity and mortality in renal transplantation is cardiovascular disease. Increased oxidative stress implies a greater degree of atherogenesis in these patients. N-acetylcysteine (NAC) which has a thiol group that is the source of l-cysteine and reduced glutathione, acts against atherosclerosis via a decrease in apoptosis, vasoconstriction, and endothelial dysfunction. Experimental models have examined the antioxidant effects of NAC during and after ischemia-reperfusion, but few studies have shown an effect in renal transplantation in human beings. In 8 months, we studied the effect of NAC treatment on oxidative stress, lipids, and renal function in 25 patients with stable renal function and no diabetes after transplantation. Data were collected on oxidative parameters: malondialdehyde, glutathione peroxidase, catalase, superoxide dismutase, glutathione reductase, lipid profile, and renal function (creatinine concentration, Cockroft-Gault formula, and Modified Diet in Renal Disease study). There were no significant differences in oxidative profile before and after treatment with NAC. The mean serum high-density lipoprotein cholesterol fraction increased after treatment and showed a significant positive correlation with glutathione peroxidase (r = 0.495). Serum creatinine concentration decreased, and Cockroft-Gault and Modified Diet in Renal Disease study estimates of renal function increased in the treatment period. In conclusion, NAC treatment in patients with stable renal function after transplantation increased high-density lipoprotein cholesterol and antioxidant molecules in relation to glutathione peroxidase, with a positive influence on renal function.