Objective To investigate the levels of serum interleukin(IL)-18 in patients with chronic renal failure (CRF)and its relationship with relevant indexes. Methods Sixty patients with CRF were divided into three groups: patients with CRF (CRF group, n = 18) ,patients with bemedialysis (HD group, n = 22) and patients with peritoneal dialysis (PD group,n = 20). 20 healthy subjects were taken as controls. The levels of serum IL-18, tumor necrosis factor (TNF)-α and high sensitivity C-reactive protein (hs-CRP) were detected by means of ELISA. Serum albumin (ALB) ,total cholesterol (TC) ,triglyceride (TG) and serum creatinine (SCr) levels were detected by con-ventional means. The GFR was measured by using the abbreviated Modification of Diet in Renal Disease study (MDRD) equation. Differences in continuous variables between the three groups were evaluated. Results The lev-els of serum IL-18 were significantly increased in CRF[(497.7 ± 120.7) ng/L], HD[(538.1 ± 113.2) ng/L] and PD[(565.7 ± 122.1) ng/L] patients than those in healthy subjects[(163.9±42.2) ng/L] (P <0.01). Further-more,serum IL-18 levels in HD patients were higher than these in CRF patients (P <0.05). Serum IL-18 levels in CRF were positively related to serum TNF-α,hs-CRP and SCr(r =0. 636,0.436,0.367,P <0.01) ,and negatively related to GFR(r = -0.515 ,P <0.05). Conclusion The levels of serum IL-18 are markedly increased in patients with CRF,HD and PD,and related to the levels of TNF-α,hs-CRP and GFR,so IL-18 might be an important marker of sub-clinical inflammation in patients with chronic renal failure.