Morphometric analysis assayed in hematoxylin/eosin stained carotid sections, and OilRedO staining on full size carotids longitudinally sectioned, revealed that carotid lesion size (apoE: 1671 ± 200 vs. NOS3/apoE: 2834 ± 286; P: 0.002), and number (apoE: 3.25 ± 1.25 vs. NOS3/apoE: 7.5 ± 1.29; P: 0.003) were significantly increased in NOS3/apoE knockout (KO) mice (Figure 2A,B), suggesting that measurement of NO might correlate with the extension of carotid atherosclerosis. The gene discussed is NOS3; the disease is carotid atherosclerosis.