It has been known that reductones in foodstuffs are capable to break down phosphodiester bondages of the highly polymerized DNA. Catecholamines such as noradrenaline, adrenaline, dopa and dopamine also belong to reductones, and all of these amines are derived in vivo from henylalanine in foods. Present paper describes the interaction of DNA and the catecholamines in coexistence with Cu^2+. 1. Oxidation of catecholamines with Cu^2+ ion was remarkably accelerated by the addition of DNA. The stimulative effect of DNA was exhibited more strongly to noradrenaline and adrenaline than dopa or dopamine. This was not necessarily correlated to their oxidation potentials. 2. Oxidized noradrenaline and adrenaline bound to macromolecular DNA, hence the DNA colored. Binding of oxidized dopa or dopamine to the DNA could not be detected in these experiments, because of their insusceptibility to the accelerating effect of the DNA. 3. These four catecholamines could also bind to the DNA without their oxidation. The binding quantities were estimated to be almost equal among these catecholamines.