Aim: To clarify the characteristics of β-adrenergic receptor subtypes in human lymphocyte and compare the competitive activities of various β-blocking agents.Methods: Lymphocyte which derived from normal volunteers were isolated by density gradient centrifugation using Ficoll-Hypaque solution. The β-adrenergic receptors were measured using hydrophilic radioligand 3H-CGP12177 and lipophilic redioligand 3H-DHA and 125 I-pindolol. The competition curves were performed in the presence of β1,β2,or β3-receptor subtype antagonist.Results: Specific binding of three radioligands were saturable. In competition curves, butoxamine, a selective β2-receptor antagonist, was much more potent in displacement of the radioligands than atenolol, a selective β1-receptor antagonist. Propranolol, a nonselective β-receptor antagonist, inhibited stereoselectively the specific binding sites with S (-)-propranolol 3~ 10 times more potent than the R (+ ) -propranolol. It is very interesting that SR59230A, a selective β3-receptor antagonist, was of some potency to displace 3H-CGP12177 and 125 I-pindolol on intact lymphocytes.Conclusion: β-Adrenergic receptors in human lymphocyte were dominated by β2-receptor subtype, but the intact cells also showed an evidence of β3-receptor subtype distribution.