Six feeding experiments with male rats which were divided into groups by low to high iodine levels in diets were carried out. Iodine intakes of individual rats were recorded daily by weighing the amount of feed supplied and remained. On the next day after final feeding, the blood was collected. Then total iodine and protein-bound iodine (PBI) in serum of individual rats were determined. As the results, significant positive correlations between serum total iodine levels and iodine intakes (r=

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... 9, p<0.001, n=126) or serum PBI levels (r=0.94, p<0.001, n=95), and between iodine intakes and serum PBI levels (r=0.94, p<0.001, n=95) were found after logarithmic transformation of these obtained values. Therefore, the regression curves (exponential functions) obtained from these results indicate that iodine intake and serum PBI levels may be calculated from the serum total iodine levels or the iodine intakes. Consequently, the serum total iodine levels should be considered to usefull in estimation of dietary iodine intakes and serum PBI levels.