Objective: Differentiated macrophages (MØ) are the resident tissue phagocytes and sentinel cells of the innate immune response. These cells are major constituents of periapical granulomas. Current studies indicate these activated cells as the source of bone-resorbing cytokines in the periapical granuloma. Periapical inflammation can be mediated by proinflammatory cytokines like interleukin 1ß (IL-1ß), tumor necrosis factor α (TNF-α), IL-6, and IL-8. Reducing the production of these cytokines may be beneficial for the treatment of periapical lesions. Oils rich in omega-3 fatty acids like docosahexaenoic acid (DHA) have been linked with anti-resorptive and bone-protective effects. The purpose of this investigation was to study the effect of DHA on the expression of these cytokines by normal and lipopolysaccharide (LPS)-treated MØ. We hypothesized that pretreatment of MØ with DHA decreases the expression of pro-inflammatory cytokines induced by LPS-treated MØ. Method and Materials: THP-1 monocytes were cultured and differentiated into MØ. DHA was added to MØ in a dose-dependent manner. MØ samples were added to the following groups: Group 1, ethanol alone as a solvent control; Group 2, 10 µg/ml of DHA (D1); Group 3, 20 µg/ml of DHA (D2); Group 4, 10 µg/ml of DHA + LPS (DL1); Group 5, 20 µg/ml of DHA + LPS (DL2); Group 6, LPS alone. Reverse transcriptase-PCR (RT-PCR) followed by ImageJ analysis was used to measure cytokine expression. Results: The results show that IL-1ß and TNF-α levels for DL and DHA (basal) were significantly lower than the levels in LPS alone. IL-6 was increased in the DL groups. There was no significant change for IL-8. Conclusion: DHA at higher concentrations may selectively decrease proinflammatory cytokine production of IL-1ß and TNF-α. More studies are needed to verify the anti-inflammatory therapeutic action of agents like DHA omega-3 fatty acids. Schlagwörter: cytokines, docosahexaenoic acid, endodontics, IL-1ß, IL-6, IL-8, inflammation, root canal, TNF-α