Sensory Characteristics of Night soil odor The effects on psychophysical coefficients. Now, attentions on sensory measurement of odor have been given to the practical evaluation in order to the control of odor pollution. This method should be brings the realistic solution of odor problems in the environment. But, several basic problems on the practical use have been unsoluting, especially, with regard to the evaluation of odor, consisting of many odorants. Standing on this point of veiw, this experimental study were carried out, in order to clear the relations between sensory intensity and compositions of odor sample, by using GLCanalysis and sensory odor test. The results obtained are as follows. 1) The psychophysical equation of Weber-Fechner is valid to the both of single component odor and complex odor, even if the composition of them changed. 2) The coefficient of W-F law (K) showed 1.43 (average) for night soil odor. And it becames clear that K values vary with the proportion of each odorant. 3) The K values of complex odor are more affected by MM, H2S and DMS than NH3 in considerably, originating in the sensory interaction of them. 4) The sensory intensity and unpleasantness of a mixed odor were also found to be correlated. When NH3 had been added to the night soil odor, unpleasantness became larger than the before it. This showed that the irritative quality of NH3 would promote considerably to the unpleasantness. 5) It is noticeable characteristics of night soil odor that odor having higher dilution/threshold, the sensory intensity of them are apt to dominated by NH3 or H2S concentrations. On the other hand, odor being lower D/T, it have been a great influenced by MM or DMS concentrations. Therefore, the practical and economical reducing to the compllaints for the night soil odor, must have the consideration to this points and will be able to perform by applying the odor neutralization.