An enzyme immunoassay for the quantitative measurement of corticosterone in serum and plasma. Corticosterone is a glucocorticoid secreted by the cortex of the adrenal gland. Corticosterone is produced in response to the stimulation of the adrenal cortex by adrenocorticotropic hormone (ACTH) and is the precursor of aldosterone. Corticosterone is a major indicator of stress since stress increases the production of corticosteroids. Studies involving corticosterone and levels of stress include impairment of long term memory retrieval1, chronic corticosterone elevation due to dietary restrictions2 and in response to burn injuries3. In addition to stress levels, corticosterone is believed to play a decisive role in sleep-wake patterns 4,5. The DRG Corticosterone ELISA Kit is a solid phase enzyme-linked immunosorbent assay (ELISA), based on the principle of competitive binding. The microtiter wells are coated with a polyclonal antibody directed towards an antigenic site on the Corticosterone molecule. Endogenous Corticosterone of a patient sample competes with a Corticosterone-horseradish peroxidase conjugate for binding to the coated antibody. After incubation the unbound conjugate is washed off. The amount of bound peroxidase conjugate is reverse proportional to the concentration of Corticosterone in the sample. After addition of the substrate solution, the intensity of colour developed is reverse proportional to the concentration of Corticosterone in the patient sample.