Psoriasis is a chronic debilitating cutaneous disorder that affects both sexes and appears clinically as inflamed, edematous skin lesions covered with a silvery white scale. Strong evidence suggests that immune mechanisms are implicated in its pathogenesis, such as persistent activation of T-lymphocytes, excessive proliferation of keratinocytes and reactivation of proto-oncogenes and other elements. Additionally, several recent studies have demonstrated that cytokines play a significant role in the pathogenesis of the disease, as they can be found in the affected skin of psoriatic patients. In this study we evaluated levels of circulating cytokines in the serum of 45 Greek psoriatic patients before initiation of treatment and compared the results with those in 45 healthy volunteers. According to our findings interleukin (IL)-2, IL-10, IL-12 and tumor necrosis factor-alpha (TNF-alpha) levels were statistically significantly elevated in the serum of psoriatic patients before therapy compared with those of controls. IL-6 serum levels did not differ between psoriatic patients and healthy volunteers. Conversely, interferon-gammaserum levels of psoriatic patients were statistically significantly lower than those of healthy volunteers.