A method for characterizing self-association of reversibly associating macromolecules in solution at high concentration in a solvent, comprising the steps of: 1. Introducing a series of k aliquots of solutions of the molecule of interest at concentrations c f, f=1...k of into a light scattering photometer, whereby said light scattering photometer i. Illuminates each injected diluted aliquot by a light beam ii. Detects the intensity of light scattered therefrom at one or more angular locations θ at which is placed a light sensitive detector; 2. Determining the concentration c f of each diluted aliquot f. 3. Forming the excess Rayleigh ratios R(c f,θ) from said detected scattered light intensities; 4. Representing said excess Rayleigh ratios to correct for thermodynamic non-ideality in terms of said k dilutions c f, f=1...k as R c f θ K = dn dc 2 ∑ i iMc f, i P i θ 1 + 2 A 2 Mc f c f − 16 π 2 3 λ 2 ∑ i c f, i 〈 r g 2 〉 sin 2 θ / 2 + 3 A 3 M ∑ i c f, i 2, wherein M is the molar mass of the monomer, i the order of each self-associating i -mer, c f,i the partial equilibrium concentration of the i-mer in the f th diluted aliquot, P i θ = 1 − 16 π 2 3 λ 2 〈 r g 2 〉 i sin 2 (θ/2), λ is the wavelength of said illuminating light beam, 〈 r g 2 〉 i the mean square radius of the i -mer, K = 4 π 2 n 2 N A λ 4, n the refractive index of said solution, N A Avogadro's number, and dn / dc the refractive increment of said macromolecule in said solution; 5. Fitting said representations of said excess Rayleigh ratios to the equations of an association model in order to determine some or all of equilibrium association constants, stoichiometries of association, incompetent fractions, second and third virial coefficients, and molar masses. 1. Introducing a series of k aliquots of solutions of the molecule of interest at concentrations c f, f=1...k of into a light scattering photometer, whereby said light scattering photometer i. Illuminates each injected diluted aliquot by a light beam ii. Detects the intensity of light scattered therefrom at one or more angular locations θ at which is placed a light sensitive detector; i. Illuminates each injected diluted aliquot by a light beam ii. Detects the intensity of light scattered therefrom at one or more angular locations θ at which is placed a light sensitive detector; 2. Determining the concentration c f of each diluted aliquot f. 3. Forming the excess Rayleigh ratios R(c f,θ) from said detected scattered light intensities; 4. Representing said excess Rayleigh ratios to correct for thermodynamic non-ideality in terms of said k dilutions c f, f=1...k as R c f θ K = dn dc 2 ∑ i iMc f, i P i θ 1 + 2 A 2 Mc f c f − 16 π 2 3 λ 2 ∑ i c f, i 〈 r g 2 〉 sin 2 θ / 2 + 3 A 3 M ∑ i c f, i 2, wherein M is the molar mass of the monomer, i the order of each self-associating i -mer, c f,i the partial equilibrium concentration of the i-mer in the f th diluted aliquot, P i θ = 1 − 16 π 2 3 λ 2 〈 r g 2 〉 i sin 2 (θ/2), λ is the wavelength of said illuminating light beam, 〈 r g 2 〉 i the mean square radius of the i -mer, K = 4 π 2 n 2 N A λ 4, n the refractive index of said solution, N A Avogadro's number, and dn / dc the refractive increment of said macromolecule in said solution; 5. Fitting said representations of said excess Rayleigh ratios to the equations of an association model in order to determine some or all of equilibrium association constants, stoichiometries of association, incompetent fractions, second and third virial coefficients, and molar masses.