The incidence of air-borne pollen grains in São Paulo city during twelve consecutive months has been studied, and the following allergic species were identified: Amaranthus spinosus L., Ambrosia polystachya DC., Chenopodium ambrosioides L., Cynodon dactylon (L.) Pers., Melinis minutiflora Beauv., Parthenium hysterophorus L., Rumex crispus L. and Solidago microglossa DC.
