Monocyte adhesion to vascular endothelium is an initial step in atherogenesis. To quantify this, we incubated monocytes with cultured endothelial cells, and quantified the adhered live monocytes using a colorimetric assay. Endothelium activated with lipopolysaccharide attracted monocytes in a dose-dependent manner and the adhesion was attenuated with post-treatments with L-ascorbic acid (53%), alpha-(40%) and gamma-tocopherol (39%), resveratrol (9%), and Lithospermum erythrorhizon root extract (45%). This non-radioactive, colorimetric assay may be useful for screening anti-atherogenic compounds in early atherogenesis.