A two-site immunoassay will be developed against apolipoprotein A-I (ApoA-I) the major apoprotein of high-density-lipoprotein (HDL). Low levels of ApoA-I have been positively correlated with coronary artery disease (CAD). To insure adequate quantification cyanogen bromide (CNBr) fragments of ApoA-I will be used to generate monoclonal antibodies (mABs) which will be selected to recognize separate epitopes on the soluble protein in untreated plasma. The assay system used will be the enzyme linked immunosorbant assay (ELISA). Quantative results from the ELISA will be correlated with other immunoassays and with assays based on direct measurement of protein mass. The ultimate goal will be to develop ELISA kits for research and clinical measurement of this important CAD risk factor.