The significance of albuminoid nitrogen was investigated and the following results were obtained. (1) When the albuminoid nitrogen and the organic nitrogen of the standard substance that represented the nitrogenous compounds in human excrement were measured, the nitrogen of organic form was recovered partly as albuminoid nitrogen but almost all recovered as organic nitrogen. (2) In the case of the waste water only one-third or one-fourth of the nitrogen of organic form was determined as albuminoid nitrogen. Especially in the case of urea only one-tenth of nitrogen could be determined as albuminoid nitrogen. (3) The correlation coefficients between albuminoid nitrogen and other determined values showed that the value of albuminoid nitrogen was significant in the case of the waste water. (4) The albuminoid nitrogen and the organic nitrogen showed the similar correlation respectively with other values in the case of the sewage in septic tank. (5) On standing for 100 days the difference between the albuminoid nitrogen and the organic nitrogen comparatively decreased after five days and then kept the nearly constant value. (6) In conclusion the albuminoid nitrogen can be used to deduce the amount of nitrogen of organic form in place of the organic nitrogen.