Psoriasis is a chronic immune and inflammatory skin disease. Fractalkine (FKN, CX3CL1), a membrane-bound CX3C chemokine, has been identified to play an important role in the pathogenesis of psoriasis. However, whether it is elevated in the tissue or peripheral blood of patients with psoriasis and is associated with disease severity is unclear. This study was carried out to explore local and serum FKN expression in patients with psoriasis and investigate the relationship with the disease severity.Serum samples were collected from 47 plaque psoriasis patients and 49 healthy individuals. Serum FKN levels were measured by an enzymelinked immunosorbent assay. The PASI scores of patients with psoriasis and their correlation with serum FKN levels were evaluated. 16 cases of local skin tissues were collected from psoriasis patients and controls who underwent traumatic incidents needing autologous skin grafting, respectively. FKN protein and mRNA expression were examined using Western blotting and RT-PCR, respectively.Local and serum expression of FKN were significantly higher than the expression in the controls (P<0.05), serum FKN levels were positively associated with Psoriasis Area and Severity Index (PASI) scores, (P<0.001) and levels of IL-22 (P<0.001) and IFN-γ (P<0.001).These results suggest that FKN may play an important role in the pathogenesis of psoriasis and represent a reliable biomarker to reflect disease severity. Therapeutic interventions that target FKN in psoriasis deserve further study.