In response to the rapid increase in odor-related complaints during the 1970s, the Japanese Ministry of the Environment developed a method for measuring lowconcentration, multi-component odorants. This method was conceptually similar to the ASTM syringe method. To overcome the limitations of small volume dilutions, odor-free 3 L polyethylene terephthalate (PET) bags were introduced. Using the triangle odor bag method, panelists were asked to identify one odorous bag among three choices, and odor concentration was determined based on each panelist’s individual threshold. Japan has also introduced an odor index, which integrates odor concentration and intensity, allowing intuitive assessment of human perception. Compared with Korea, differences exist in panelist selection, reference odor intensity levels, the number of panelists required, and threshold calculations, leading to variations in measured odor concentrations. Since the early 2000s, comparative studies have demonstrated that the Japanese method is comparable to European olfactory measurement practices. The triangle odor bag method has been recently become widely adopted across Asia, while dynamic olfactometry has been standardized under ISO standards, facilitating international harmonization of odor measurement and regulatory frameworks. This study provides an overview of the Japanese olfactory measurement method and the procedure for calculating the odor index.