The P and Y values were relatively high at 94.3 gl, corresponding yo the Q value, nitrogen sources were supplemented. In YE3 and YE6, the P, Y and sugar consumption were not significantly different from those of the control treatment, but the Q values increased to 3.14 and 3.89 gl h , respectively. In Thailand, the cost of yeast extract, and dried spent yeast are approximately US 100 and 1 per kg, respectively, were employed. The results showed that the P, Q and Y values of DSY4.5 and DSY9 were similar to those of YE3 and YE6, respectively. The Q values of DSY4.5 and DSY9 were 3.11 and 3.92 gl h , respectively. These results clearly indicated that both nitrogen supplements did not have a positive effect on yeast growth but they promoted the rate of ethanol production or the ethanol productivity under the high gravity fermentation. Although the total nitrogen content of YE3 and YE6 were equal to those of DSY4.5 and DSY9, respectively, the initial assimilable nitrogen contents were different (table 1).