In Japan, discussions on the regulation and labeling of trans-fat (TF) have under way for several years in the Food Safety Commission and the Consumer Affairs Agency. However, administrative measures for TF have not yet been taken, partly because of the insufficiency of scientific data in Japan. To provide data about the TF intake by Japanese, we determined the levels of TF contained in total diet samples and in food samples that were served as individual meals (one-serving samples). We analyzed 5 groups of total diet samples prepared in 11 regions throughout Japan, and 5 categories of one-serving samples using the GC-method after verifying its performance. The estimated daily intake of TF based on the analytical results of the total diet samples was around 500 mg and no significant difference was observed in the intake of the TF among the 11 surveyed regions. On the other hand, many one-serving samples classified into “hamburger”, “pizza” and “Western food” categories contained more than 500 mg of TF per serving, the standard value in the labeling regulation in the United States. If these one-serving meals are taken to represent one meal out of 3 in a day, the intake of TF can easily be expected to exceed the daily intake estimated through the analysis of the total diet samples.