introduction. Exposure to airborne pollen from certain plants can cause allergic disease, but allergens can also be found in non-pollen-bearing fractions of ambient air. This may explain why the allergic response in susceptible patients does not always coincide with the presence and magnitude of airborne pollen counts. Plantago pollen is an important cause of pollinosis in northern Mediterranean countries, but it is difficult to determine its incidence in allergies because Plantago pollen appears in the atmosphere at the same time as grass pollen. objective. The study aimed to investigate the relationship between the atmospheric concentration of Pla l 1 aeroallergen and Plantago pollen, and its incidence in a population group. materials and method. Pollen was sampled using a Hirst-type volumetric trap (Burkard™) and Burkard Cyclone sampler (Burkard™) for Pla l 1 allergen. Allergen was determined with a Pla l 1-specific ELISA. Serum-specific IgE levels to several plant allergens were measured with the EAST system. results. The aerobiological dynamics of Plantago pollen grains and Pla l 1 did not follow the same trend, whereas the sum of Plantago with some other pollen types showed a more similar behaviour. Of the 118 subjects tested, sera from 52 contained IgE to Plantago pollen, but only 5 were monosensitized. conclusions. The presence of Pla l 1 in the atmosphere depends not only on Plantago pollen but also on the pollen of other species from the Oleaceae family. Knowledge of the behaviour of allergen Pla l 1 in the atmosphere can help understand better asthma exacerbations associated with aeroallergens.