IL-23-dependent IL-17-producing T helper (Th) lymphocytes are associated with autoimmunity. We investigated the immunopathological mechanisms for activation of Th17 cells of patients with systemic lupus erythematosus (SLE). Concentration of cytokines/chemokine in plasma and culture supernatant from SLE patients and healthy controls were measured by ELISA or flow cytometry. Plasma IL-12, IL-17, IL-23 and CXCL10 concentrations and the number of Th17 cells were significantly elevated in SLE patients than control subjects (both p<0.05). Elevated IL-12, IL-17 and CXCL10 concentrations correlated positively and significantly with SLEDAI (all p<0.05). Plasma IL-12 and IL-17 showed significant and positive correlation with plasma Th1 chemokine CXCL10 concentration in SLE patients (all p<0.05). Ex vivo inductions of IL-17 by IL-23 or IL-18 from co-stimulated lymphocytes were significantly higher in SLE patients than controls (all p<0.05). The activated IL-23/IL-17 axis is important for the inflammatory immunity in SLE.