Potassium iodide, sodium iodide, and Iod-Ethamine were given by stomach tube to 54 rabbits and the concentration of alcohol-soluble and -insoluble blood iodine followed for a period up to 24 hr. Following all three iodides, there was a rise and fall in the values of both fractions of blood iodine, the values for the alcohol-soluble fraction rising to the higher levels but declining more rapidly than the values for the alcohol-insoluble fraction. Potassium iodide had the advantage over sodium iodide that after its use the peak levels of both fractions of blood iodine were maintained for a longer period of time. Iod-Ethamine had the advantage over potassium iodide that higher peak levels were reached with both fractions of blood iodine and, while not maintained for as long as after potassium iodide, these peak levels were held for several hours and for a longer period than following sodium iodide. The concentrations of blood iodine were of the same order or higher than those found in respiratory tract fluid following administration of the same dose of iodides, suggesting that the appearance of iodine-containing substances in respiratory tract fluid (R.T.F.) after iodide therapy is of the nature of a simple diffusion from blood.