Hydrolyzable and condensed tannins are representatives of a large group of polyphenolic compounds found in plants. There is great interest in the importance and function of these compounds in plant-predator relationships. The identification of and characterization of these molecules from plant materials could greatly increase the likelihood of elucidating a role and mechanism of action. Cotyledons and embryo of the Quercus palustris acorn were pulverized with a mortar and pestle after removing the seed coat. Tannins were extracted from this material and subjected to ESI/LC/MS. The tannins were identified based upon the fragmentation patterns and comparison with prior work. The concentration of the individual tannins in the developing Quercus palustris acorn was followed throughout the growing season to observe the effect of maturation.