Folate coenzymes are involved in one-carbon transfer reactions needed for the synthesis of nucleic acids, amino acids, and proteins which are very important for cell proliferation and differentiation. To investigate the effects of dietary folate content on plasma and tissue folate concentrations and on folate excretions in urine and feces, male Sprague-Dawley rats were raised for 4-10 weeks on semi-purified experimental diets containing 0mg, 2 mg, 8mg folate/kg diet. Folate concentrations were determined microbiologically using Lactobacillius casei (ATCC 7469). When compared to the folate adequate diet, the folate deficient diet decreased folate levels in plasma, liver and kidney , and the values were further decreased with experimental period. In rats reviving folate supplemented diets, plasma , liver and kidney folate adequate or supplemented diets, folate concentrations weer increased compared to animals on the folate adequate diet. In the folate adequate or supplemented diets, folate concentrations in the plasma and kidney were maintained at essentially the same level for 10 weeks . Folate concentrations in the liver, however, continued to increase with experimental period. Dietary folate intake seems to influence plasma and liver folate concentrations more than kidney folate concentrations. Folate excretions unrine and feces were significantly increased with dietary foalte intakes and experimental period. Folate excreted via urine was consideerably greater than that via feces. These resutls indicated that the foate supplemented diet improved plasma and tissue foalte status. Whether folate supplmentation improves foalte-dependent reactions remains to be researched.