In addition to the classical TH1 and TH2 cytokines, members of the recently identified IL‐17 cytokine family play an important role in regulating cellular and humoral immune responses. At present nothing is known about the role of these cytokines in atherosclerosis. Expression of IL‐17A, ‐E and ‐F was investigated in atherosclerotic tissue by rtPCR and immunohistochemistry. IL‐17E and its receptor were further studied in cultured smooth muscle cells and endothelial cells, using rtPCR and western blot. rtPCR showed that IL‐17A, ‐E and ‐F were expressed in the majority of plaques under investigation. IL‐17A/F was expressed by mast cells in all stages of plaque development. IL‐17A/F⁺ neutrophils were always observed in complicated plaques, but hardly in intact lesions. IL‐17A/F⁺ Tcells (‘TH17’) were never observed. IL‐17E was expressed by smooth muscle cells and endothelial cells in both normal and atherosclerotic arteries, and in advanced plaques also extensively by mature B cells. Cultured smooth muscle cells and endothelial cells were found to express both IL‐17E and its functional receptor (IL‐17RB). The constitutive expression of IL‐17E by resident plaque cells, and the additional presence of IL‐17E⁺ B cells and IL‐17A/F⁺ neutrophils in advanced and complicated plaques indicates a complex contribution of IL‐17 family cytokines in human atherosclerosis, depending on the stage and activity of the disease. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.