Stimulation of beta(2)-adrenergic receptors on the cell surface by adrenaline or noradrenaline leads to alterations in the metabolism, excitability, differentiation and growth of many cell types. These effects have traditionally been thought to be mediated exclusively by receptor activation of intracellular G proteins(1). However, certain physiological effects of beta(2)-adrenergic receptor stimulation, notably the regulation of cellular pH by modulation of Na+/H+ exchanger (NHE) function, do not seem to be entirely dependent on G-protein activation(2-7). We report here a direct agonist-promoted association of the beta(2)-adrenergic receptor with the Na+/H+ exchanger regulatory factor (NHERF), a protein that regulates the activity of the Na+/H+ exchanger type 3 (NHE3)(8). NHERF binds to the beta(2)-adrenergic receptor by means of a PDZ-domain-mediated interaction with the last few residues of the carboxy-terminal cytoplasmic domain of the receptor. Mutation of the final residue of the beta(2)-adrenergic receptor from leucine to alanine abolishes the receptor＇s interaction with NHERF and also markedly alters beta(2)-adrenergic receptor regulation of NHE3 in cells without altering receptor-mediated activation of adenylyl cyclase. Our findings indicate that agonist-defendent beta(2)-adrenergic receptor binding of NHERF plays a role in beta(2)-adrenergic receptor-mediated regulation of Na+/H+ exchange.