Abstract—Five inbred strains of mice differing in susceptibility to diet-induced atherosclerosis were compared for neointimal hyperplasia after endothelial denudation with an epoxy resin--modified catheter probe. Results showed that all animals responded similarly to the arterial injury, with increased medial area and thickness after 14 days. In contrast, a significant strain-specific difference in neointimal formation after injury was observed. The atherosclerosis-susceptible C57L/J mice were also susceptible to injury-induced neointimal hyperplasia, and the C3H mice were resistant to both forms of vascular diseases. The 129/Sv mice, which displayed an intermediate level of diet-induced atherosclerosis, also displayed an intermediate level of injury-induced neointimal hyperplasia. Interestingly, the atherosclerosis-susceptible C57BL/6 mice were resistant to neointimal hyperplasia after endothelial denudation, whereas the atherosclerosis-resistant FVB/N mice were susceptible, displaying massive neointimal hyperplasia after arterial injury. All (C57L/JxC57BL/6)F₁ hybrid mice were resistant to injury-induced neointimal hyperplasia. Moreover, N₂ mice generated from backcrossing the F₁ hybrid mice to the susceptible C57L/J mice displayed a range of arterial response to injury, spanning the most severe to the most resistant phenotype. These results indicate that injury-induced neointimal hyperplasia and diet-induced atherosclerosis are controlled by distinct sets of genes; the former appeared to be determined by recessive genes at 2 loci.