AbstractA separate consideration of ligand‐β‐adrenoceptor interactions responsible for affinity (recognition, binding) and agonistic activity, respectively, is very important for the explanation of molecular events eliciting the activating conformational change of the receptor. Equilibrium models of β‐adrenergic effectuation including receptor activation by agonists and partial agonists, receptor‐effector (G‐protein) coupling, and adenylate cyclase stimulation allow to obtain LFER‐related parameters of both interaction components from apparent dissociation constants and intrinsic activities. Two models, both containing “precoupling” of non‐activated receptor and effector molecules, are derived: a ternary complex model for the interaction of ligands, receptor, and effector in the absence, and an adenylate cyclase activation model for enzyme activation in the presence of GTP. Agonistic activity is represented by the equilibrium constant K* reflecting the concentration ratio of activated and non‐activated agonist‐receptor complexes. KD, the dissociation constant of non‐activated complexes, represents ligand‐receptor recognition and binding. K* can be estimated either from using ratios KL/KHof apparent low‐ and high affinity dissociation constants in GTP absence, or from using intrinsic activities of adenylate cyclase activation. According to our models, KL, which also describes apparent dissociation in binding assays with GTP, is related to KDand K* with KL= KD/(1 + K*). In terms of the free energy of ligand binding and receptor activation. ΔG° = RT ln KL, this corresponds to a decomposition of pKLinto pKL= pKD+ log (1 + K*). In QSAR, thus, log (1 + K*) is the parameter of choice for LFER‐related description of ligand‐receptor intera