Methods are described for the analysis of NMR data for systems in which complex formation with 2:1 stoichiometry takes place. Criteria for the reliability of the parameters obtained from the analysis are formulated. From simulation of typical cases it appears that normally two sets of experiments, one with each of the components held at a fixed concentration and the other varied, will provide an adequate description of the system within certain limits determined by the nature of the system. This approach is then applied to the DMSO-Eu(fod)3 system in carbon tetrachloride. It is found that the limiting shifts of the 1:1 and 2:1 adducts, respectively, are 447 ± 11 and 275 ± 65 Hz, and the dissociation constants are 0.75 ± 0.06 and 24.0 ± 1.7 mM. These parameters reproduce the data to within 2.4%.