Human Osteopontin kit is designed to quantitatively measure human Osteopontin present in biological samples and tissue culture media. A human Osteopontin standard is provided to generate a standard curve for the assay. Standards or diluted samples are pipetted into a clear microtiter plate coated with a monoclonal antibody to capture Osteopontin. After a 60 minute incubation, the plate is washed and a peroxidase conjugated Osteopontin monoclonal antibody is added. The plate is again incubated for 60 minutes and washed. Substrate is then added to the plate, which reacts with the bound Osteopontin Antibody Conjugate. After a short incubation, the reaction is stopped and the intensity of the generated color is read at 450 nm.