Adrenergic innervation of the atrioventricular valves in the carp Cyprinus carpo, frog Rana temporaria, tortoise Emys orbicularis, hens and albino rats has been investigated by histochemical glyoxylic technique. It was shown that the adrenergic innervation of cardiac valves becomes more intense and more complex during progressive evolution of cardio-vascular activity. Adrenergic nerves realize the connection between annullus fibrosus, valve, chordal tendineal and papillary muscles. Chromaffin cells of the valve serve as an additional store of catecholamines. A possibility cannot be excluded that these cells supply with biogenic amines the papillary muscles regulating their activity.