Besides the variety of other cellular processes in which beta-adrenergic compounds have been involved, their effect on the second messenger cAMP is thought to be related to the growth and differentiation of malignant cells. Because beta-adrenergic receptor could be an easy target for a new combination treatment, we attempted to identify and characterize adrenergic receptor in breast tumor and sought for correlations with estradiol and progesterone receptors. Using L[3H]-dihydroalprenolol, a potent beta-adrenergic antagonist, we demonstrated in human breast tumor the presence of beta-adrenergic receptors with high affinity (Kd 1-3 nM) as shown by Scatchard analyses. Natural and synthetic agonists and antagonists inhibited the [3H] DHA binding, mainly in the order of beta 2-subtype potency. We verified that these receptors were normally coupled with G-protein. A slight correlation was shown between adrenergic and progesterone receptors, and no correlation between adrenergic and estrogen receptors. The presence of specific beta-adrenergic receptors functionally coupled with G protein incited us to study their physiological regulation, since it is tempting to speculate that circulating or locally released catecholamines or other natural compounds may participate in the process of growth and differentiation of the mammary gland through adrenergic receptors.