The aim of this study was to preliminarily assess the effect of enrichment of meadow sward through direct undersowing with hybrids of grasses from the Lolium-Festuca complex on their share in sward a year after treatment and on the quality of produced fodder. Studies started in 2016 in Helenowo (Żuławy Elbląskie) on permanent meadow situated on alluvial soil. The meadow was dominated by Dactylis glomerata (L). and Poa pratensis (L.) with a small share of Festuca pratensis (Huds.), Elymus repens (L.) and Phleum pratensis (L.). The meadow was undersown with selected varieties of two hybrids: Festulolium braunii (var. Paulita+Felopa and Perun) and Festulolium pabulare (var. Brečva and Hykor). After initially good sprouting, seedlings of studied Festulolium varieties started to die out. The highest resistance to unfavourable pluviothermal conditions was found in Perun variety, smaller - in varieties Brečva and Hykor and the lowest in Paulita+Felopa varieties sown in a mixture (25% of complete sowing each). The yield of undersown meadow sward in the year of treatment depended mostly on floristic composition of sward and only slightly - on selected Festulolium variety. Natural composition of sward and the frequency of mowing were the main factors affecting nutritive value of sward. Potential milk production from fodder of studied sward was 12.4 thous. kg · ha^-1 when meadow was mown 4 times and 11.3 thous. kg · ha^-1 at 3-time mowing.