Abstract:The calculation of pollen concentration has become a standard method in pollen analysis. Heavy liquid floating usually produces clean and pollenrich preparations. Pollen loss in this process can affect results of calculation of pollen concentration by exotic pollen method. These effects are evaluated quantitatively in this paper. The errors caused by floating vary from 1 to 15 per cent approximately, depending on the specific gravities of heavy liquid used in preparation and different pollen sizes.