Catecholamines are a group o f compounds identified by the catechol nucleus. The significant catecholamines found naturally in the body are epinephrine, nor- epinephrine and dopam ine. They are found in various tissues o f the body like brain, adrenals, GIT, blood, urine and cerebrospinal fluid in picogram quantities. K now ledge o f catecholam ines is im portant in the diagnosis and m anagem ent o f pheochrom ocytom a, CNS tum ours like neuroblastom a, Diabetes m ellitus, hypertension, coronary disease, angina pectoris, m yocardial infarction etc. A nalytical techniques for determ ination o f catecholam ines have been developed w hich are gen erally based u p o n the use o f iso lated enzym e catech o l-O -m ethyltransferase (C O M T ) to tran sfer a radioactive m ethyl group from S-adenosyl-L-m ethionine (SAM ) to an endogenous catecholam ine acceptor m olecule to form a radioactive O -m ethyl catecholam ine derivative. This article gives a basic out line o f the catecholam ine assay along w ith a sim plified protocol th at can be easily perform ed in the laboratory.