We studied sheep grazing preferences and effect of defoliation activities on the plant species composition within the context of reintroduction of farming activities in the eastern part of Giant Mountains (Klínové boudy enclave). Grazing preferences of sheep developed during vegetation seasons. Differences between two consecutive years were caused by experiences of grazers and partly by changes in the vegetation of the grazed area caused by introduction of defoliation. Defoliation activities caused reduction of tall dominants Senecio ovatus, S. hercynicus, Epilobium angustifolium, Rubus idaeus and Hypericum maculatum.