Aim. The aim of this study was to determine tumor necrosis factor-alpha (TNF-α) levels in periapical exudates and to evaluate their relationship with radiological findings. Methodology. Periapical exudates were collected from root canals of 60 single-rooted teeth using absorbent paper points. TNF-α levels were determined by enzyme-linked immunosorbent assays. The samples were divided into three groups according to the periapical radiolucent area. Results. Nonparametric Kruskal-Wallis test revealed significant differences between TNF-α concentrations in control group (40, 57±28, 15 pg/mL) and group with larger radiolucent areas (2365, 79±582, 95 pg/mL), as well as between control and canals with small radiolucent areas (507, 66±278, 97) (P<.05). Conclusions. The levels of TNF-α increase significantly in teeth with periapical pathosis, from smaller to bigger lesions. This research and its results have shown that objective analysis of the TNF-α levels enables establishment of a relationship between different concentrations of TNF-α and different radiological changes.