Nornal human adults taking a diet without meat, fish, peas or beans excrete no creatine in the urine. The exceptions to this thus far observed are the appearance of small amounts of creatine in women during the menstrual period (1) and the creatinuria in women reported by Denis and Minot (2) following the ingestion of a high protein diet. Creatine is found in the urine of individuals suffering from wasting diseases, starvation, during carbohydrate deprivation, diabetes mellitus, poisoning by phlorhizin, hydrazine, adrenalin and sodium selenite, exophthalmic goiter, fevers and the muscular atrophies and dystrophies (3). The presence of creatine in the urine in pathological conditions is considered evidence of abnormal endogenous nitrogen metabolism of muscles. Shaffer (4) reports 0.18 gram of creatine nitrogen in the twenty-four-hour urine of patients ill with exophthalmic goiter. Of the several pathological conditions studied by Shaffer only in the post partum period did he encounter values in excess of this. Associated with the abnormal creatine excretion in exophthalmic goiter there was a reduced excretion of creatiniine. Normally the daily excretion of creatinine nitrogen per kilogram of body weight amounts to 7 to 11 mgm., whereas in the cases of goiter only 3 to 6 mgm. are excreted.Since the creatine-creatinine metabolism is apparently of great significance in normal muscle function the known disturbance of this phase of metabolism in exophthalmic goiter on the one hand and the effect of iodine administration in reducing basal metabolism and im-1 A brief abstract of this work was presented before the Society for Experimental Biology and Medicine.