Modulation of macrophage functions by fatty acids (FA) has been studied by several groups, but the role of cell death in these effects has not been examined yet. In the present study, the cytotoxicity of palmitic, stearic, oleic, linoleic, arachidonic, docosahexaenoic and eicosapentaenoic acids on a macrophage cell line (J774) was investigated. The induction of toxicity was investigated by changes in cell size, granularity, membrane integrity and DNA fragmentation by using flow cytometry. Fluorescence microscopy was used to determine the type of cell death (acridine orange/ethidium bromide assay). The possible mechanisms involved were examined by measuring mitochondrial depolarization, lipid accumulation and PPARγ activation. The results demonstrate that fatty acids induce apoptosis and necrosis of J774 cells. The cytotoxicity of the fatty acids was not strictly related to the number of double bonds in the molecules: palmitic acid > docosahexaenoic acid > stearic acid = eicosapentaenoic acid = arachidonic acid > oleic acid > linoleic acid. The induction of cell death did not involve PPARγ activation. The mechanisms of FA to induce cell death involved changes in mitochondrial transmembrane potential and intracellular neutral lipid accumulation. Fatty acids poorly incorporated into triacylglycerol showed the highest toxicity. These results indicate that the anti-inflammatory effects of ω-3 FA supplementation, recommended for patients with rheumatoid arthritis and other chronic inflammatory diseases, may be related to their ability to induce macrophage death.