In order to measure alcohol related problems, it is fundamental task to begin with to know the drinking quantity of the people. This study tries to explore the comparative, methodological possibilities of Timeline Follow Back (TLFB) as well as Self-Monitoring (SM) methods to measure drinking quantity, using the sample of Japanese and Sri Lankans. Especially TLFB method has not being so far utilized in Japan for this purpose. This pilot study has done in two stages. In the first stage, it has focused to get data on the correct drinking quantity up to two months period. After analyzing data of the first pilot survey, it was decided to reduce in the second-staged study the time frame to obtain data on drinking quantity only up to one month period. In the second-staged study, 37 Japanese and 36 Sri Lankans living in Japan has been selected. Results show that it is more appropriate SM method than TLFB method to investigate drinking quantity of the Japanese. Further it was evidenced that in order to employ TLFB method to investigate correct drinking quantity of the general Japanese population, it has to be further improved for overcoming ambiguity of respondents' memory on their alcohol consuming behavior. Moreover, it is understood that some characteristic drinking behaviors, influenced by Japanese drinking culture may be another barrier in getting correct drinking quantity data. However, the hypothesized notion of this cultural barriers was not supported. An alternative hypothesis "reflexive sensitivity to drinking", was implied.