Zoosporic and conidial fungi species and environmental factors in 12 various sites of the River Biebrza in Biebrza National Park were studied. Samples of water were collected in autumn 1999 and spring 2000 for hydrochemical analysis in order to determine the number of fungal species. Buckwheat-seeds, hemp-seeds, cellophane and snake exuviae were used as bait during exposure in a laboratory. 199 lower aquatic fungus species were found in various sites of the River Biebrza. 16 species were recorded for the first time from Poland.