Based on the recent proposal that the Cl- concentration in night soil of 5500 ppm used as standard should be re-examined 87 samples of night soil were selected at random from night soil treatment plants iu Gifu Prefecture over a 9-month period and their Cl- concentration was measured by the mercuric nitrate method, using 1000-fold diluted solution, which was found to be the best method for this analysis. Mean and standard deviation of Cl- concentration were 5362 and 864 ppm, respectively. There was no statistically significant difference in the mean values between cities and in monthly variations, at the 5% level of significance. The values of x^-±σ and x^-±2σ for the 86 samples eliminating the critical values were calculated, and 76.7 and 91.8% of the samples were in these respective ranges. Cl- concentration in night soil differs according to the ratio of urine to feces, and this concentration in urine differs according to the water intake, amount of respiration, and food intake of the people, but the present experiments demonstrated that the value of 5500 ppm is representative as the standard of Cl- concentration in night soil.