In absence of β‐receptor blocking agents, α‐adrenergic inotropic effects could be demonstrated in the rat myocardium for the synthetic α‐agonists phenylephrine and methoxamine, but not for the naturally occurring catecholamines, adrenaline and noradrenaline. Other synthetic α‐agonists were without effects. In the presence of the β‐receptor blocking agent, propranolol or timolol, marked α‐effects were demonstrated for adrenaline and noradrenaline in both the right and left atria and the right ventricle. The results indicate that α‐receptors may be functionally important in the