THE NUMBER of studies on fat-splitting enzymes in the urine is very small. Papers on urinary enzymes in general hardly mention the possibility of their presence. The methods used are open to objection. It is, therefore, not surprising that the results are contradictory. The latest and rather comprehensive German paper, by Zorn,1published in 1937, denies the presence of a fat-splitting enzyme in the urine of healthy persons. In the American literature of the past 20 years we did not find any reference except for a citation of Zorn in Bockus' "Handbook of Gastroenterology."2 In our early investigation of pancreatic enzymes in blood and urine under normal, pathological, and experimentally produced conditions in men and animals3we developed a method for the determination of a fat-splitting enzyme in the blood and adapted it for the use in the urine. The principle of the method is that lipase splits olive