This experiment was canied out to investigate the effect of pasture types(mixture and mono tall fescue pasture) and endophyte infection on the dry matter yield, forage quality and animal performance of pasture plants at the Experimental Field of Grassland and Forage Crops Division, National Livestock Research Institute, Suweon, in 1994. The results obtained are surmmarized as follows : DM yield of tall fescue monoculture was significantly higher(p<0.05) than that of mixture pasture, while DM yield of endophyte-infected pasture was significantly higher(p<0.05) than that of endophyte-free for two pasture types. Crude protein yield(CPY) of tall fescue monoculture was significantly higher(p<0.05) than that of mixture, and the higher CPY with endophyte-infect tall fescue for both pasture types resulted from higher DM yield of the pastures. NDF and ADF contents of pasture plants were not influenced by pasture types, and there was no difference for NDF and ADF contents between endophyte-infect and -free pasture mixture, however, those of pasture plants were increased with endophyte-infect tall fescue in monoculture. IVDMD of pasture plants was increased with mixture and endophyte-free tall fescue for both pasture types. IVDMD of pasture plants was greatly influenced by pasture types and endophyte infection. There were no significant differences in average daily gain of Korean native cattle between pasture types, but those of the cattle were significantly increased with endophyte-free tall fescue for both pasture types(p<0.05). Based on the results of this experiment, it is suggested that a slightly more forage yield could be obtained , from monoculture and endophyte-infected tall fescue. However, liveweight gain was increased by mixture and endophyte-free tall fescue with good quality.