The pollen concentration in the atmosphere of Caxias do Sul was studied using the volumetric suction Hirst-type sampler (Burkard model), during 2001 and 2002. During the study period, 40 pollen types were identified and 18 of these were selected to compose the Pollen Calendar: Amaranthus, Araucaria, Asteraceae, Carya, Cupressaceae, Cyperaceae, Ligustrum, Melastomataceae, Mimosa scabrella, Myrsine, Myrtaceae, Pinaceae, Plantago, Poaceae, Ricinus, Rumex, Sorocea and Urticaceae, which account for 97% of the total pollen content. Clearly distinct pollen seasons were observed, with the highest concen-trations of pollen grains in winter and spring.

El an?lisis de la concentraci?n de polen en la atm?sfera de Caxias do Sul fue realizado durante los a?os 2001 y 2002 usando un captador volum?trico de succi?n tipo Hirst. Durante el periodo de estudio se han identificado 40 tipos pol?nicos diferentes. Los 18 siguientes constituyen el 97% del contenido de polen total y el calendario pol?nico: Amaranthus, Araucaria, Asteraceae, Carya, Cupressaceae, Cyperaceae, Ligustrum, Melas-tomataceae, Mimosa scabrella, Myrsine, Myrtaceae, Pinaceae, Plantago, Poaceae, Ricinus, Rumex, Sorocea y Urticaceae. Las mayores concentraciones pol?nicas se registran durante los meses de invierno y primavera.