It was attempted in this study to assess the vitamin $B_{1},;B_{2}$, and $B_6$ status in tissue by determination of erythrocyte transketolase (TK), glutathione reductase (GR), and aspartate aminotransferase (AST) activities, and their activation by their respective coenzymes, thiamine pyrophosphate, flavin-adenine dinucleotide, and pyridoxal-5-phosphate. The activities of erythrocyte enzymes were stable for more than 30 days when erythrocyte had been stored at $-20^{circ}C$ and affirmed that the enzyme activities were more stable in the case of deep frozen sotrage of erythrocytes rather than hemolysates. The assay procedures involving ultraviolet kinetic analysis with continuous monitoring for each of enzymes have good within-batch and between-batch precisions and will be avalable in the routine laboratories for the nutritional and clinical surveys. Activity coefficient of TK, GR, and AST was studied in healthy medical students (fifteen men and twelve women, between 21 and 30 years old) on an unrestricted diet. The mean activity coefficient of TK, GR, and AST were 1.18, 1.35, and 2.01 for men, and 1.14, 1.33, and 1.83 for women, respectively. And the upper limit of normal (mean+2SD) were 1.52, 1.69, and 2.61 for men, and 1.50, 1.61, and 2.37 for women, respectively.