Psoriasis was initially considered to represent a disease of abnormal epidermal keratinocyte proliferation. Proliferation of keratinocytes is restricted by apoptotic cell death to maintain a constant thickness of epidermis. Nucleosomes are mainly released by apoptotic cells. Tumor necrosis factor-alpha (TNF-alpha) is an important factor affecting the apoptosis. In the present study, the relationship between TNF-alpha, nucleosome and the Psoriasis Area and Severity Index (PASI) score was investigated. The patients were divided according to PASI score into three groups (mild, moderately, severe). Serum TNF-alpha and nucleosome levels were measured using Enzyme-linked immunosorbent assay (ELISA) method. Our findings show a correct relationship between PASI scores and TNF-alpha and an inverse relationship between nucleosome and PASI score. According to the results obtained from the study, we believe that serum nucleosome levels can be used as a new indicator in follow-up of patients with psoriasis and monitoring of the effectiveness of drugs which used in the treatment of psoriasis.