Immunological mechanisms play an important role in the pathogenesis of atherosclerosis and atherosclerotic abdominal aortic aneurysms (AAA). Inflammatory leukocytes invade the vessel wall and produce cytokines which perpetuate the immune events underlying these diseases. Interleukin (IL)-1 beta, IL-8, tumor necrosis factor-alpha, and monocyte chemoattractant protein-1, among others, may play a role in the generation by AAA. The aim of this study was to investigate the possible pathogenetic role of other proinflammatory cytokines, namely IL-2, IL-4, IL-6, and interferon (IFN)-gamma. Enzyme-linked immunosorbent assay of human explant culture supernatants revealed a significant increase in IFN-gamma production by AAA compared to occlusive (atherosclerotic) or normal (NL) aortic explants. IL-6 production was also increased in AAA compared to NL aortic explant supernatants. Neither AAA nor NL aortic tissues produced IL-2 or IL-4 in the same culture system. These results suggest that IL-6, a cytokine involved in T and B lymphocyte activation during inflammation, and IFN-gamma, which stimulates T and B lymphocytes, macrophages, endothelial cells and fibroblasts, may play a role in the pathogenesis of various vascular inflammatory diseases such as AAA.