A comparative study on the muscle proteins of beef (female Japanese brown cattle: Diabhragma, Pars muscularis) and chicken (male Kimber strain broiler: M. pectoralis major) was performeed, the meat samples stored at 4℃ for 24 hours after slaughtering being used. In the present experiment, besides investigations on the condition of extracting muscle proteins, the water holding capacity, the nitrogen distribution, ultracentrifugal and starch gel electrophoretic analyses of muscle proteins were undertaken. The results obtained are as follows; 1. A maximum amount of nitrogen was extracted from each of beef and chicken in the 0.1 M borate buffer solution of pH 7.5 when the NaCl concentrations of which were 1.4 M for the former and 1.8 M for the latter. Therefore, muscle proteins were extracted under the above conditions of extracting the maximum amount of nitrogen in the present work throughout. 2. The contents of actomyosin N and myosin N in beef were significantly lower than those in chicken, while the contents of non-protein N and stroma N in the former were remarkably higher than those in the latter. 3. The water holding capacity of chicken was considerably better as compared with that of beef, though their pH values were almost the same. 4. In the ultracentrifugal analyses, 4 peaks were observed in the patterns of both meat samples, but the sedimentation constants for chicken were fairly greater than those for beef. 5. According to the results of starch gel electrophoretic analyses treated with urea a lone and both urea and β-mercaptoethanol, beef and chicken differed in the number of zones separated and in the movement of some zones. Nevertheless, further investigations are necessary to throw light on the distinct and detailed differences in the properties of muscle proteins between beef and chicken by starch gel electrophoresis.