In order to find the relationship between the quality of silage and its constituents, especially ammonia nitrogen content, samples of silage obtained from dairyfarms at Tsuyama city, Okayama prefecture in Japan, were analyzed. In each sample, the moisture content, total nitrogen, and ammonia nitrogen as well as pH value were determined by the usual method. The following are some of the results obtained: It was found that the mean value of the dry matter of these samples was 21.61 ± 4.90 per cent. The mean value of ammonia nitrogen content was 334.4 ± 170.5mg per cent. A significant negative correlation, γ=-0.615, was found between the pH value and the lactic acid content (p<0.001). Significant positive correlations were found between the pH value and the ammonia nitrogen content of the silages; and they are shown in the following table: The regression equation was y=11.27 x-33.43, where x=pH value and y=ammonia nitrogen in per cent. of total nitrogen. It was found that the ammonia nitrogen in per cent. of the total nitrogen was an important, if not the sole, criterion for deciding the quality of silage. The results of pH measurements with Toyoroshi pH-test paper were compared with those obtained with Iio's glass electrode pH-meter. The application of pH-test paper for the estimation of pH value of silage seems to give significantly lower values than that of the pH-meter (Difference 0.1 ; p<0.001). The results of estimation of moisture in silages by means of an oven-drying method were compared with those obtained with the distillation method. The results obtained by the former method were always higher than those by the latter method.