Systemic Lupus Erythematosus is a complex disorder that occurs as a consequence of a number of independent processes and factors, most likely an autoimmune process caused by an imbalance of T helper cell cytokines resulting in an abnormal immune response.The pattern of cytokine production can be defined as Th1, Th2 or Th3 response. Interleukin-18, formerly known as IFN-γ inducing factor, is a member of the IL-1 family that plays an important role in the Th1 responses. Previous studies have shown that the level of IL-18 in SLE patients was high compared to healthy controls and that this rise correlated with disease activity in SLE patients, suggesting a potential pathogenic role of IL-18 in SLE. Patients and Methods: Forty-one SLE patients and twenty age and sex matching controls were included in the study. We investigated the serum level of the pro-inflammatory Th1 cytokine IL-18 in serum samples from patients and controls using ELISA technique. Serum level of IL-18 was correlated with SLEDAI score and other disease parameters.Results: Serum level of IL-18 was significantly higher in SLE patients with a mean serum level of 620.51+443.35 pg/ml compared to that in healthy controls having a mean serum IL-18 of 97.80+49.28 pg/ml (p= 0.0001). Furthermore, Serum level of IL-18 highly correlated positively and significantly with SLEDAI score (p= 0.006). Conclusion: The Th1 pro-inflammatory cytokine, IL-18 might play a crucial role in triggering the inflammatory process in SLE.