The experiments supported jointly by National Renderers Association, Far East Office and Korea Mixed Feed Association were conducted in three different poultry farms in or vicinity of Seoul, Korea. The objectives were to demonstrate the economic and nutritional value of using tallow as a feed ingredient in formulating the isocaloric and high energy broiler rations. It was also to determine the dietary level of tallow which is most feasible for the economy of broiler production in Korea. on an Isocaloric Basis The use of tallow to replace corn on an isocaloric basis upto 9 percent level did not improve the growth over the control chicks. Little significant difference was also observed in the feed efficiency of control group from those of the experimental groups of receiving 3, 6 and 9 percent tallow. This is also true for the values of among the experimental groups. Through the observations of these results, it is concluded that tallow as a feed ingredient can be added to the diet upto 9 percent level on an isocaloric basis without any deteriorating effects on it`s nutritive value. The addition of tallow to the place of corn on an isocaloric basis resulted in higher prices of the feeds of added tallow. Since little improvement on the feed efficiency was gotten by adding tallow, it is assumed that the economic broiler production is rather solely depended upon the price of tallow rather than the value of tallow itself. on a High Energy Basis On the contrary from that of isocaloric basis, all three experimental groups of receiving tallow are responded favorably over the control group. As for the weight at the end of 8 weeks of feeding, broilers receiving 7% tallow gained 10.0%, and 7.6% for the semibroilers over the control group. Cumulative feed efficiency for the broiler indicate that all the experimental groups receiving tallow improved to compare to that of control. For the groups receiving 5 and 7% tallow, the efficiency was 2.11 for the 5% and 2.04 for the 7% group compared to that of control 2.46 For the semibroilers, efficiency was 2.25 for the 5% and 2.21 for the 7% tallow compared to that of control 2.46. These differences from that of control were statistically significant. The analysis on the economic return indicate that the return for all experimental groups receiving tallow, except for the 7% tallow group of semibroilers, was greater than that of control. The best economic return was attained for the group receiving 5% tallow with increase of 8.4% return for the broiler and 6.1% for the semibroiler.