The CO-derivative of myoglobin obtained by the method described in the previous report and that of haemoglobin were observed spectrophotometrically. Light absorption spectra of these two typical haemoprotains showed no difference in various species of animals. However, there was a considerable difference between light absorption spectra of CO-myoglobin and those of CO-hemoglobin, since in the former the maximum was recorded at 577, 540∼541 mμand the minimum at 560 mμ, while in the latter the maximum was recorded at 570, 539∼540 mμand the minimum at 555 mμ. A nomogram was made (Fig. 4) by means of this difference between CO-myoglobin and CO-haemoglobin, and by using this nomogram, myoglobin contents of muscles of different species of amounts of total red pigments in the meat were determined. It has been proved that the amount of total red pigments in the meat decreases in horse meat, beef mutton and pork in this order and that a considerable difference exists among different muscles of the same individual. The myoglobin content of the red muscle pigment increases with the increase of total pigments, in other words, the deeper the red color of meat, the more myoglobin is contained in the meat.