Disclosed is an assay (method) to quantify the amounts of catecholamine-O-methyltransferase (COMT) protein in samples, such as extracts from cell cultures, body fluids, tissues, and environmental samples. It uses novel agents (anti-NE, COMT-NE, or COMT-epitope-NE) in combination with two previously described agents (anti-COMT and COMT) in a competitive ELISA system to achieve this aim.