The introduction of a range of different genetic modifications in mice results in altered lipoprotein metabolism and the development of vascular lipid lesions. At present, however, it is unclear to what extent the molecular events underlying lipid lesion formation are similar in these different mouse models of atherosclerosis. The aim of this study was to compare the protein expression pattern of lipid lesions from seven different mouse lines with varying susceptibility to vascular lipid lesion development, to determine to what extent lesions induced by different genetic interventions have a similar composition. The proteins we have measured, using quantitative immunofluorescence, are proteins whose expression is known to be modulated during atherogenesis in humans, including plasminogen activator inhibitor (PAI)-1, transforming growth factor (TGF)-β1, osteopontin and the macrophage marker CD11b. In all the mice lines we have investigated, PAI-1 was elevated wherever lesions developed. Active TGF-β was depressed in the vessel wall of mice which developed lipid lesions, particularly in the intima. In contrast, TGF-β1 antigen (active plus latent TGF-β1) was increased at lesion sites. Accumulation of osteopontin and, with the marked exception of apolipoprotein(a) transgenic mice, tissue macrophages occurred at sites of lipid deposition in the vessel wall. Each lesion, irrespective of its size and the mouse strain in which it developed, had similar amounts of PAI-1, active TGF-β and osteopontin per unit area of lesion. These data are consistent with a common phenotype accompanying atherogenesis, irrespective of the genetic basis of susceptibility.