The Corticosterone (High Sensitivity) EIA kit is a competitive enzymeimmunoassay utilising a polyclonal corticosterone antibody coated onto the inner surface of polystyrene microtitre wells. Heat treated Calibrators, Controls and samples are incubated with enzyme (horseradish peroxidase) labelled corticosterone in the antibody coated wells for 4 hours at room temperature. The wells are washed and colour is developed using a chromogenic substrate (TMB). The absorbance of the stopped reaction mixtures are read in a microplate plate reader, colour intensity developed being inversely proportional to the concentration of corticosterone.