Iodine balance was studied in 3-day periods for 15 days on three subjects, nine on a fourth, and six on a fifth. The combined urine and stool iodine may account for less than 50 per cent of the iodine intake. There was a fairly uniform output of iodine for an individual on a monotonous diet. The fecal iodine was higher in these studies than in those of Scheffer and von Fellenberg. In two subjects studied Scheffer's observation of an increased fecal iodine in hyperthyroidism was confirmed.