Results of chemical analyses on residues collected from ceramic vessels found in an early Classic period Maya tomb revealed that certain of the residues contained theobromine and caffeine, a clear indication that the corresponding vessels once contained cacao in some form. Of the vessels yielding cacao residues, one is decorated with hieroglyphs, two of which are believed to have the phonetic values for the word cacao in the Mayan language. These findings are significant for three reasons: 1) a new method for recognizing ancient cacao use is demonstrated, 2) a novel way of verifying glyph interpretations is presented, and 3) data are generated that indicate what contents certain Maya vessels actually held, thus permitting useful functional interpretations.