Wound treatment practices of the Aztecs are discussed. The use of concentrated maguey sap (Agave ssp.) was widely dispersed and has persisted in folk medicine. A possible reason may be that it is effective. Laboratory analysis of maguey syrup indicates that its utilization as a remedy by ancient and modern Mesoamericans could contribute to the healing process of aerobic wound infections. Both pyogenic and enteric bacteria appear to be susceptible to maguey syrup. The traditional addition of salt to the remedy seems to enhance the effectiveness of the material in inhibiting the growth of one of the major causes of pus-forming or pyogenic infective processes, Staphylococcus aureus. This finding is additional proof of the effectiveness of pre-Hispanic medicine, and of the skills of pre-Hispanic physicians.