Riboflavin in the various materials which used for Takju brewing was determined and its quantitative changes in the Takju mashes which were mashed with polished rice and wheat flour respectively using Nuruk only for enzyme source, and with wheat flour and corn powder respectively using Nuruk and Koji, were checked at 24 hours intervals during the whole brewing period. The results obtained were as follows. a) The riboflavin contents in 100 grams of each materials were: Polished rice 46.9γ Wheat flour 67.3γ Corn powder 73.9γ Nuruk 169.0γ Koji of wheat flour 87.1γ Koji of corn powder 84.4γ b) About 30 to 40 percent of riboflavin in the polished rice, wheat flour and corn powder were losed by steaming at 10 pounds for 50 minutes. c) Riboflavin content in the plots used Nuruk only was decreased during 3 days after mashing and then increased markedly after 5 days and, more or less, decreased after 6 days. Quantitative changes of riboflavin in the plots used Nuruk and Koji showed a rugged curve without decreasing in early stages, and its content was also increased markedly 5 days after mashing and then decreased a little after 6 days. d) Approximately 82γ of riboflavin was determined in 100㎖. of the ripened mash of the rice plot and 72γ in the wheat flour plot in the case of using Nuruk only. 88.6γ of riboflavin were determined in 100㎖. of the ripened mash of the wheat flour plot and 83.6γ in the corn powder plot in the case of using Nuruk and Koji. e) It was assumed that 28.8γ to 41γ of riboflavin were contained in 100 ㎖. of finished Takju of the two plots used Nuruk only and 33.6 to 44.5γ in the both two plots used Nuruk and Koji. f) About 47.3γ of riboflavin were determined in 100 grams of Takju cake of the rice plot and 66.2γ in the wheat flour plot used Nuruk only, and 62.9γ in the corn powder plot and 64.5γ in the wheat flour plot used Nuruk and Koji.