The aim of the study was to analyse the ragweed (Ambrosia) pollination in Szczecin (western Poland) in the years 2000-2002. Measurements were performed by the volumetric and gravimetric method. Pollen seasons were defined as the periods of 90 % of the total catch. Ragweed pollen is known as a very potent aeroallergen. In recent years ragweed appeared in Europe in hitherto unknown localities, and the number of people allergic to the allergens of this plant has been gradually increasing. In the period of the study a strong tendency towards increasing ragweed pollen counts in the air of Szczecin was noted. Of the three years studied, the lowest concentration of ragweed pollen observed in 2000 equalled a few pollen grains in 1 m(3) per 24 h. In 2001, the highest airborne concentration of 30 grains in 1 m(3) per 24 h was noted at the end of August. The annual pollen count of ragweed in 2002 was 3 times higher than in 2001. The pollen season started in the second decade of August and lasted until the beginning of September. The highest airborne concentration of 98 grains in 1 m(3) per 24 h was noted at the beginning of September on a sunny day with strong wind. The pollen count of ragweed was found to depend on the weather conditions, especially on wind speed and relative humidity, diversity of local flora and long distance transportation.