Medical Ethnobotany of the Yucatec Maya: Healers' Consensus as a Quantitative Criterion. Economic Botany 53(2):144-160, 1999. There is an urgent need to obtain information on the relative importance of a taxon used medicinally as compared to others within the same culture. This was achieved through a documentation of the current indigenous medical uses of 320 species in three Yucatec Maya communities during 18 months of fieldwork. The 1549 individual reports documented were divided into nine groups, which classify indigenous uses. The frequency of usage of the individual plants reported was employed in the analysis of the ethnobotanical importance of the respective taxa. Species cited more frequently in a group of indigenous uses are regarded to be of greater ethnobotanical importance than those cited only by a few informants. In order to obtain information on possible biological, pharmacological and toxicological effects of some particularly important species, the scientific literature on these taxa was evaluated systematically. The study is the basis for phytochemical and pharmacological evaluations of the traditional use