The impact of ruminant even-toed ungulate game – red deer (Cervus elaphus), sika deer (Cervus nippon), fallow deer (Dama dama), mouflon (Ovis musimon), roe deer (Capreolus capreolus) and chamois (Rupicapra rupicapra) living in the open on the condition and development of forest ecosystems in some national nature reserves was studied in 2000 and 2001. The national nature reserves included into the project were NNR Vývěry Punkvy, NNR Praděd, NNR Vrapač, NNR Týřov, NNR Jezevčí vrch, NNR Karlštejn and NNR Břehyně-Pecopala. The browsing damage (% of damaged individuals in the total number of trees up to 2m height) was measured in deciduous species. The studies showed that browsing damage to broadleaves remains a significant limiting factor for evolution of the forest ecosystems in some regions. In three of the studied reserves, viz. NNR Týřov, NNR Břehyně-Pecopala, and NNR Praděd, browsing reaches intensities which put into danger the set-up goals of protection in these landscape areas. In other two localities – NNR Vývěry Punkvy and NNR Vrapač – browsing has become a significant factor. There are only two nature reserves – NNR Karlštejn and NNR Jezevčí vrch – where browsing does not considerably affect the growth of the tree-layer.