The current "gold-standard" for quantitative assessment of steatorrhea, 72-h stool fat, is universally recommended in evaluation of malabsorption but vastly under-utilized because it is tedious and difficult to perform. We propose a novel approach for direct measurement of steatorrhea from all causes which eliminates the limitations of the 72-h stool test while retaining its important features. Our approach is based on administration of 1,3--[13C]distearyl, 2-oleolyl glycerol and the nonabsorbable marker DyCI3 with a high fat meal followed by analysis of a single stool. The test is expected to be sensitive to steatorrhea of maldigestion and fatty acid malabsorption, cost effective, and to provide results that are highly correlated with 72-h stool fat in individual patients. During Phase I, we demonstrated the feasibility of the approach by showing that Dy is quantitatively excreted and follows the same excretion kinetics as 13C- labeled triglyceride. During Phase II, we will study details of the approach leading to a practical test for clinical use. We will demonstrate that labeled triglyceride absorption is reproducible, accurately reflects the degree of steatorrhea in individual patients, and has excellent diagnostic sensitivity/specificity. The developed test kit and analytical services will be marketed through BioChemAnalysis Corporation. PROPOSED COMMERCIAL APPLICATION: This research will lead to the availability of a test kit and procedure for accurate quantitation of steatorrhea from all causes and requires collection of only a single stool. Because the procedure highly reproducible, accurate and relatively simple to use it will be applicable to clinical diagnostic use as well as use in research.