Bacterial infection of the pulp results in the development of a periapical lesion with the concomitant resorption of periapical bone. The cytokines are believed to play an important role in this matter. The purpose of this study was to find the relationship among the presence of black pigmented bacteria, the levels of cytokines(TNF-${alpha}$, -${eta}$, IL-$1{eta}$, and TGF-${eta}1$), and the amount of bone resorption in periapical and pulpal diseases. For the purpose, the patients were grouped into chronic apical pathosis, acute apical pathosis, acute pulpitis, and a healthy control group. Root canal samples were taken from periapical tissue exudates during routine endodontic treatment, and the venous blood was taken from each patients. The samples were processed to measure local and systemic levels of the cytokines using enzyme linked immunosorbent assay(ELISA). Bacterial content of Porphyromonas endodontalis, Porphyromonas gingivalis, and Prevotella nigrescens were measured by indirect immunofluorescence method and the size of the periapical lesions were measured from the radiographs. The following results were obtained: 1. The levels of bone resorptive cytokines(TNF-${alpha}$, TNF-${eta}$, and IL-$1{eta}$) in exudates from acute and chronic apical pathoses were significantly higher than those from acute pulpitis and the normal pulps(p<0.05). 2. IL-$1{eta}$ were the highest among the bone resorptive cytokines in apical pathoses. However, no statistical difference between acute and chronic lesions were found(p>0.05). 3. The levels of TGF-${eta}1$ in exudates from acute pulpitis and chronic apical pathoses were significantly higher than those from acute apical pathoses and the normal pulps(p<0.05). However, there were no significant correlations among the levels of bone resorptive cytokines. 4. The levels of TNF-${eta}$ in serum were significantly higher than those from the exudates while serum TGF-${eta}1$ concentrations were significantly lower(p<0.05). 5. Exudates from the canals in which the P. nigrescens were detected showed significantly higher levels of IL-$1{eta}$ than those from the canals without the microorganism(p<0.05). 6. There were no significant correlations among the levels of the cytokines, the amount of bone destruction, and the presence of acute and chronic symptoms(p>0.05).