Over the past twenty five years the Commission on Equilibrium Data of the Analytical Division of the International Union of Pure and Applied Chemistry has been sponsoring a noncritical compilation of metal complex formation constants and related equilibrium constants. This work was extensive in scope and resulted in publication of two large volumes of Stability Constants by the Chemical Society (London). The first volume, edited by L. G. Sillen (for inorganic ligands) and by A. E. Martell (for organic ligands), was published in 1964 and covered the literature through 1962. The second volume, subtitled Supplement No. 1, edited by L. G. Sillen and E. Hogfeldt (for inorganic ligands), and A. E. Martell and R. M. Smith (for organic ligands), was published in 1971 and covered the literature up to 1969. These two large compilations attempted to cover all papers in the field related to metal complex equilibria (heats, entropies, and free energies). Most recently a noncritical compilation of organic ligands by D. D. Perrin (Pergamon Press) extended coverage of the literature through 1973 and a similar volume for inorganic ligands by E. Hogfeldt covered through 1974. Since it was the policy of the Commission during that period to avoid decisions concerning the quality and reliability of the published work, th~ compilation would frequently contain from ten to twenty values for a single equilibrium constant.