In the first paper of this series1we showed that a fat-splitting enzyme is present regularly in the urine of dogs. In addition, we presented evidence that the fat-splitting enzyme is of pancreatic origin. Our conclusion is based on the following findings: 1. Injection of mecholyl and secretin increases the amount of fat-splitting enzyme in the urine. 2. Removal of the pancreas causes an immediate disappearance of the enzyme in the urine. 3. Ligation of the pancreatic ducts leads to a marked rise in the excreted amount of the enzyme followed slowly by a decrease to rather low levels. 4. Pancreatectomy is followed by the disappearance of the fat-splitting enzyme from the urine. 5. Ligation of the ducts followed by pancreatectomy causes an immediate disappearance of the high values of the enzyme in the urine. These experimental findings formed the basis for studies on urinary lipase in man. The