The pathology and pathologic physiology of celiac disease remain obscure in spite of the many attempts that have been made to understand them. It has become clearer in recent years that celiac disease is a clinical picture "characterized by arrest of growth, a distended abdomen, and attacks of diarrhoea with large, pale, foul-smelling stools" 1 rather than a disease entity and that the underlying pathologic condition may differ in different cases.2 A tradition exists that pancreatic steatorrhea can be readily differentiated from idiopathic steatorrhea by the low percentage of split fat in the stools associated with the former and the normal percentage characterizing the latter. A careful survey of the literature, however, reveals few cases of either disease in which careful clinical observations have been followed by adequate postmortem examination. The present study was initiated because of the findings in case 44 (XX), in which a patient with celiac disease who had a high percentage of split fat in the stools and who had responded favorably to treatment for celiac disease was found at autopsy to have cystic fibrosis of the pancreas. This demonstrated that the recognized criteria of differentiation between the steatorrhea due to pancreatic insufficiency and that due to other causes are unreliable.To establish more reliable criteria it is necessary to study cases in which normal acinar tissue has been proved by postmortem examination to be absent or inadequate and to compare them with cases of celiac disease associated with a normal pancreas. The plan of the present investigation has been to collect the cases in which pancreatic insuffi¬ ciency has been proved by microscopic examination of the pancreas, to