The importance of Grass (Poaceae) pollen as a cause of hay fever in the South-Plain of Hungary was studied by aeropalinological and allergological methods. Since 1989 the pollen counting has been performed with the help of a Lanzoni VPPS 2000 sampler. On the basis of the pollen counting the second most important allergen pollen of this region are the grass pollen. From 1989 to 1995 skin prick tests (Soluprick, Epipharm) were performed in 642 patients with seasonal allergic rhinitis. 261 of these patients suffer from hay fever in May and June when the daily pollen count of grass pollen is the highest. The skin prick tests of these 261 patients were positive to Poaceae in 84%, and to Secale in 63%. But 57% of the patients was allergic to both Poaceae and Secale, so the exact allergen research is very important before hyposensitisation. Ragweed (63%) and Mugwort (33%) sensitivity was found also in high percent of the grasspollinosis patients with symptoms during the late summer season too.