Physicochemical studies on po1ynuc1eotides and their components are a relatively new field which, almost daily, attracts an ever­ increasing number of scientists. To date, however, only a limited effort has been made to compile the vast amount of physicochemical data available into a useful format. I originally undertook this compilation of data to supplement my own research efforts. But it soon became evident that my labors might be of benefit to other workers in this complex area, and this volume is the result. The information cited in this manuscript covers the literature up to the end of 1970. The present compilation cannot possibly list all recorded dissociation constants, extinction coefficients, and Tm values of po1ynuc1eotides, oligonucleotides, and their com­ plexes. As outlined in the "Explanation of Tables," some discre­ tion had to be exercised in the selection of oligonucleotides and po1ynuc1eotides for inclusion. Every effort has been made, however, to provide more than just a representative cross section of the available literature.