Performance evaluation methods and criteria for trans-fatty acids analysis using GC-FID were examined. The measurement method constructed in this study was based on the American Oil Chemists' Society (AOCS) official standard methods Ce1h-05. The method for fat extraction from general foods was based on the methods for nutrition labeling notified by the Ministry of Health, Labour and Welfare of Japan and AOAC 996.06. To estimate trueness and precision, fortified samples were analyzed following the established experimental design. Five molecular species of trans-fatty acids that are rarely contained in foods were used for preparing the fortified samples. To estimate precision, more than four degrees of freedom of variance are required. Based on the results, within-laboratory trueness and reproducibility will be set at 90–110% and 10% (RSD%), respectively.