Abstract: Methods involving the use of mathematical models of competitive ligand-receptor binding to characterize mixtures of ligands in terms of compositions and properties of the component ligands have been developed. The associated mathematical equations explicitly relate component ligand physical-chemical properties and mole fractions to measurable properties of the mixture including steady state binding activity, 1/Kd,apparent or equivalently 1/EC50, and kinetic rate constants kon,apparent and koff,apparent allowing; 1) component ligand physical property determination and 2) mixture property predictions. Additionally, mathematical equations accounting for combinatorial considerations associated with ligand assembly are used to compute ligand mole fractions.