Apolipoprotein B (ApoB) is the primary protein constituent of low density lipoprotein, very-low density lipoprotein, and chylomicrons. ApoB directs cholesterol and triglyceride containing particles to tissues by ApoB receptor binding and internalization. The ratio of ApoA1 to Apolipoprotein B (ApoB), the primary component of low density lipoprotein, is an effective predictor of cardiovascular disease. The sensitive quantitative measurement of total human ApoB antigen in plasma, serum, urine and other biological fluid samples is easily performed with this 96 well strip format ELISA kit. ApoB is present in human plasma and serum at a concentration of 0.5-1.25 mg/ml in adult males, 0.45-1.2 mg/ml in adult females, 0.11-0.31 mg/ml in newborns, and 0.23-1.39 mg/ml in children. The ratio of ApoA1/ApoB ranges from 0.85-2.24 in males and 0.76-3.23 in females. The assay measures total human ApoB in the 5-5000 ng/ml range. Samples giving human ApoB levels above 5000 ng/ml should be diluted in diluent before use. A 1:20,000 to 1:80,000 dilution for normal human plasma is suggested for best results. Human ApoB will bind to the affinity purified capture antibody coated on the microtiter plate. After appropriate washing steps, monoclonal anti-human ApoB primary antibody binds to the captured protein. Excess primary antibody is washed away and bound antibody is reacted with the peroxidase conjugated secondary antibody. Following an additional washing step, TMB substrate is used for color development at 450nm. A standard calibration curve is prepared along with the samples to be measured using dilutions of human ApoB. Color development is proportional to the concentration of total ApoB antigen in the samples. All reagents and standards are provided in these ELISA kits.