In order to investigate the effect of feeding monensin on the feed intake, nutrient utilization and ruminal fermentation characteristics, 12 Korean native uncastrated male goats were randomly allotted to 0,22 and 33 ppm monensin treatment. Complete rations, consisted of 80% concentrate and 20% ground orchard grass hay, were offered once a day. Ad libitum feed intakes of each were measured and 80% of that amount were offered during the metabolism trial. Monensin decreased dry matter intake significantly(p≤.05). Digestibility of dry matter, crude fiber, NDF and energy were increased(p≤.05) by feeding monensin. These tendencies of reduced dry matter intake and digestibility improvement were more drastic in 22 ppm than 33 ppm monensin level. Monensin feeding did not affect the nitrogen retention. As the monensin level increased, the ruminal propionic acid concentration also increased(p≤.05), and the butyric acid content and A/P(acetic acid/propionic acid) ratio decreased(p≤.05). In monensin-fed goat, the ruminal pH and microbial protein concentration increased (p≤.05);however, no trend was found in the ruminal viscosity and NH₃-N concentration, and NH₃-N and urea-N concentration in the plasma. It is concluded that monensin-fed goats consumed less feed thereby causing probable the improvement in feed efficiency. Thus, monensin appeared to be a useful feed additive, directing the rumen fermentation in a more productive way.