In addition to hazel pollen, alder pollen causes allergy symptoms in subjects suffering from early spring allergies. The study consisted in the analysis of the concentration of Alnus pollen in the air of 12 Polish cities: Bialystok, Bydgoszcz, Cracow, Kielce, Lublin, Olsztyn, Piotrkow Trybunalski, Sosnowiec, Szczecin, Warsaw, Wroclaw, and Zielona Gora. The research was carried out in 2022. The volumetric method and Burkard or Lanzoni samplers were used. The pollen season was determined with the 95% method. The onset of the season was recorded earlier in the west of Poland than in the east of the country, i.e. between January 30th and February 18th. The season ended between March 23rd and April 3rd. The maximum alder pollen concentrations were determined in between February 14th and March 16th. The highest concentrations of alder pollen were detected in Kielce and Piotrkow Trybunalski, while the lowest values were recorded in Bialystok and Szczecin.