Background:Lupus nephritis (LN) is a debilitating complication of systemic lupus erythematosus (SLE). Renal biopsy is the gold standard for evaluating LN. Serum C4d is a potential non-invasive method for evaluating LN. The purpose of this study was to evaluate the value of C4d in the assessment of LN.Methods:This cross-sectional study was conducted on patients with LN who were referred to a tertiary hospital in Mashhad, Iran. Subjects were divided into four groups including LN, SLE without renal involvement, chronic kidney disease (CKD) and healthy controls. Serum C4d. creatinine, and glomerular filtration rate (GFR) were assessed for all subjects.Results:Forty-three subjects (11, 25.6% healthy controls, 9, 20.9% SLE patients, 13, 30.2% LN and 10, 23.3% CKD patients) participated in this study. CKD group were significantly older than other groups (p>0.05). There was a significant difference in gender distribution between groups (p<0.001). Median serum C4d were 0.6 in healthy controls and CKD group and 0.3 in SLE and LN groups. There was no significant difference in serum C4d between groups (p=0.503).Conclusion:The findings of this study indicated that serum C4d might not be a promising marker in the assessment of LN. These findings should be documented by further multicenter studies.