Standard reference ranges for all laboratory test values are mandatory. This study was designed to establish a reference range for blood vitamin B₁ levels, since the normal range has not been determined in the Japanese population. We founded the Japan Committee for Vitamin Laboratory Standards, which was incorporated with the Vitamin Society of Japan and the Japanese Society of Nutrition and Food Science. We standardized whole blood vitamin B₁ levels using three HPLC techniques (post-calumn reverse-phase HPLC, pre-column reverse-phase HPLC, and precolumn GP-HPLC). The reference range was obtained in 54 volunteers administered a 1, 800 kcal diet with 2mg of vitamin B₁ (1.74mg measured) daily to avoid marginat vitamin B₁ deficiency in the population. The range for each assay was 26-47ng/ ml, 28-51ng/ml, and 28-56ng/ml, respectively. Our data suggest that 26-28ng/ml is the lower limit of normal for whole blood vitamin B₁, but further studies in a larger population are needed in order to obtain more definitive results.