Background: One of the major immunological problems is SLE (systemic lupus erythematosus)and lupus nephritis is one of the main complications, INF (interferon) plays an important role in disease pathogenesis Aim of the work: The aim of this work to assess the level of INF gamma in sufferers with lupus nephritis in comparison to patients with non-nephritis lupus and their correlation to the disease activity. Patients and methods: This research was conducted on 60 persons divided into two groups: group I (group SLE) comprising 40 patients, 20 patients with nephritis and 20 patients without nephritis, and group II (control group) comprising 20 age-matched normal control persons. Disease activity assessed in patients' SLEDAI (SLE Disease Activity Index) and sera and controls were tested for the INF gamma level measured in the Human INF GAMMA ELISA (Enzyme-Linked Immunosorbent Assay) kits. Results: In the SLE group, serum levels of INF gamma were substantially higher than in the control group and also higher in patients with nephritis than in non-nephritis group and had direct correlation with SLEDAI score, level of anti-ds DNA(anti double stranded DNA) and proteinuria. Conclusion: For SLE patients, INF gamma may be used as a biomarker, and it is higher in renal activity .