Objective: Neopterin (NT) is a compound of low molecule-based pteridine. It is secreted by macrophages as a response to the stimulation of cytokines such as interferon-gamma, interferon-1beta, tumor necrosis factor alpha or bacteria compounds such as lipopolysaccharides. Procalcitonin (PCT) levels may increase in the course of bacterial, parasitic, and fungal infections. Therefore, it can be used for the differential diagnosis of the infection, especially in cases of serious inflammation. In this study, the role of NT, and PCT in sepsis as a prognostic factor, and the relationship between the two parameters are examined., Methods: From November 1, 2005 through December 31, 2005, fifty patients with sepsis admitted to the Department of the Infectious Diseases and Clinical Microbiology and/or Department of Anaesthesiology and Reanimation were enrolled in the study. Patients were divided in two subgroups according to their survival: group I (n=23) nonsurviving patients and group II (n=27) surviving patients., Results: Serum NT levels have been found to be increased in group I (median: 15 ng/mL, range: 2-69) when compared to group II (median: 5 ng/mL, range: 2-130). The difference was statistically significant (P=0.03). Other laboratory parameters and PCT levels (group I median: 0.13; group II median: 0.08; P<0.05) were not different between the two groups., Conclusions: NT was found to be a prognostic factor in patients with sepsis.