Background: Some of the common AR gene polymorphisms results in alteration of their receptor functions. But, the effects of these polymorphisms on the efficacy of adrenergic agonists are not yet well established. Hypothesis: We assessed the hypothesis that the efficacy of, dobutamine (DBU), a representative beta-agonist, would be affected by AR genotypes - alpha2cDel322-325, beta1Gly389Arg, beta2Arg16Gly and beta2Gln27Glu. Methods and results: We prospectively enrolled 105 patients, who underwent dobutamine stress echocardiography (DSE), and determined their AR genotypes. Fifty six patients with normal DSE, who were not taking beta-blocker, were allocated to ���normal group��� and 49 patients with previous myocardial infarction who were taking beta-blocker were allocated to ���MI group���. We measured the changes in heart rate, blood pressure, left ventricular ejection fraction (LVEF) and mitral annular velocity, in response to dobutamine infusion at the rate of 5, 10 and 20 microgram/kg/min. In the normal group, presence of the alpha2cDel322-325 allele and age were significant determinants of change of cardiac contractility, measured by LVEF, in response to dobutamine infusion, both in univariate and multivariate analysis. (table1) But, the effect of DBU on heart rate and blood pressure were not significantly affected by the genotype. In MI group, the effects of AR polymorphisms were not significant. The usage of beta-blockers might alter the effect of AR gene polymorphism in this group Conclusion: The alpha2cDel322-325 AR polymorphism was an important genetic determinant of efficacy of DBU. The use of beta-agonist, such as DBU, might be individualized according to their AR genotypes and status of beta-blocker usage.