Investigations with artificial inoculation of soil and grain of 12 oats genotypes with Drechslera avenae isolate no 1 were carried out in years 2000-2002 on experimental plots near Zamość. In each year the number of 7-weeks seedlings, number of plants and panicles before harvest, and grains yield from the individual plot were calculated. The greatest mean seedling loss after three years of investigations when compared to the control was 47.8% (‘Akt’), and the lowest 13.0% (‘Bajka’), while the loss of plants before harvest ranged from 15.8% (‘Bajka’) to 52.6% (‘Bachmat’). The mean decrease in panicle number compared to the control ranged from 4.2% (‘Bajka’) to 45.5% (‘Jawor’) and mean grain yield loss was lowest in ‘Borowiak’ (18.4%) and ‘Bajka’ (22.8%), while highest in ‘Akt’ (70.3%). Mycological analysis of grains obtained from oat plants developed from caryopses subjected previously to artificial infection with Drechslera avenae under field conditions revealed a considerable number of this pathogen isolates. On average isolates of Drechslera avenae accounted for 59.0% of the total number of fungi isolated from surface-sterilized grains and 48.7% from non-sterilized grains. From both surface-sterilized and non-sterilized control grains, most frequently were isolated: A. alternata, B. sorokiniana, F. culmorum, F. graminearum, F. oxysporum, F. poae, F. sporotrichioides and P. verrucosum var. cyclopium.