Lipolysis and adenylyl cyclase (AC) activation in response to β‐adrenergic agents are abnormally low in white epididymal adipose tissue (WAT) of the ob/ob mouse. The abundance of G‐proteins (G_sα and G_iα) linked to AC is also abnormally low. By contrast, β‐adrenergic receptor (β‐AR) levels were previously found to be normal in WAT and elevated in liver. The relative importance of various forms of the β‐AR in mouse WAT was reassessed in view of the discovery of the β₃‐AR. The results show that (1) the β₃‐AR is mainly responsible for AC activation in lean‐mouse WAT; (2) the β₃‐AR is only partly responsible for AC activation in obese mouse WAT; and (3) GTP modulates β₃—‐but not β₁—‐or β₂‐AR activation of AC in a biphasic manner. Therefore, the β₃‐AR appears responsible for the well‐known bimodal effect of GTP on β‐adrenergic receptor‐mediated AC activity in WAT.