Atherosclerosis is a consequence of lipid deposition and foam cell formation in the arterial wall. Macrophage scavenger receptor A II is involved in the uptake of modified low density lipoproteins. It contains an extracellular conserved lysine cluster which has been proposed to form a positively charged groove that interacts with acetylated low density lipoproteins (AcLDL). This study evaluated the role of the murine SRA-II and a lysine mutated SRA-II on AcLDL uptake. Fluorescence labeled AcLDL uptake was quantified using a Laser Scan Cytometer. A significant increase in fluorescence uptake was found in the cells transfected with SRA-II versus those with empty vector. Cells expressing the lysine mutated SRA-II also demonstrated a significant decrease in their uptake of AcLDL. This data supports the concept that the conserved lysine cluster in murine SRA-II is the binding region for AcLDL or contributes to the trimeric structure of SRA-II necessary for AcLDL binding.