Live specimens of the adult field frog Rana arvalis were collected from northeastern Poland during their reproductive season. Histological diagnosis was positive in two of the seven specimens for chytridiomycosis caused by Batrachochytrium dendrobatidis. Different stages of pathogen–immature, mature with zoospores, empty and collapsed–were identified. Large numbers of sporangia were found in the toes and forepart of the abdomen of the frog. This is the second report of chytridiomycosis in R. arvalis in Europe and the first in Poland.