Following oral admn. of 1.0 [mu]g. of Co60 vit. B12, seven normal persons excreted 12-59% of radioactive cobalt in the stool in 3-9 days. No activity could be found in the urine of 2 normal subjects up to 8 days after ingestion of the vitamin. Four patients with pernicious anemia in remission excreted 89-99% of the dose in the stool. In 3 of these cases 2 mg. of folic acid, 10 mg. of folic acid for 1 week, 50 g. of ventriculin, and 15 mg. of intrinsic factor had no appreciable effect on the amt. ex-creted. In one case 2 mg. of folic acid and 15 mg. of intrinsic factor reduced the excretion of Co60 about 40%, and 50 g. of ventriculin cut the fecal activity about 25%. In 3 patients 2 g. of aureomycin for one week had no effect and 150 cc. of neutralized normal gastric juice reduced the fecal activity about 30%.