Amino acid-amino acid interaction energies have been derived from crystal structure data for a number of years. Here is reported the first derivation of normalized relative interaction from binding data for each of the four bases interacting with a specific amino acid, utilizing data from combinatorial multiplex ONA binding of zinc finger domains [Desjarlais, J. R. and Berg, J. M. (1994) Proc. Natl. Acad. Sci. USA, 91, 11099–11103]. The five strongest Interactions are observed for lysine-guanine, lysine-thymine, arginine- guanine, aspartic acid-cytosine and asparagineadenine. These rankings for interactions with the four bases appear to be related to base-amino acid partial charges. Also, similar normalized relative interaction energies are derived by using DNA binding data for Cro and X repressors and the R2R3 c-Myb protein domain [Takeda, Y., Sarai, A. and Rivera, V. M. (1989) Proc. Natl. Acad. Sci. USA, 86, 439–443; Sarai, A. and Takeda, Y. (1989) Proc. Natl. Acad. Sci. USA, 86, 6513–6517; Ogata, K. et al. (1995) submitted]. These energies correlate well with the combinatorial multiplex energies, and the strongest cases are similar between the two sets. They also correlate well with similar relative interaction energies derived directly from frequencies of bases in the bacteriophage X operator sequences. These results suggest that such potentials are general and that extensive combinatorial binding studies can be used to derive potential energies for DNA-protein interactions.