ROYAL NORTHERN HOSPITAL" A DISEASE of the terminal ileum, affecting young adults, characterized by a subacute or chronic necrotizing and cicatrizing inflammation, ulceration of the mucosa and excessive connective tissue formation through the wall, leading to stenosis and fistula formation ". In these words Crohn,l in 1932, described a localized disease of the ileum of a granulomatous nature, and gave it the name "regional ileitis".Since that time it has become evident that other parts of the intestinal tract may become involved in such a process. Harris, Bell, and BrunnY2 in 1933, recorded the involvement of the jejunum only, and in 1934 C01p3 described the first example in which large and small bowel were together affected. Many other cases have recently been described, some being earlier examples of obscure intestinal granulomata reviewed in the light of Crohn's researches, and others being recent types conforming to the entity which he described. Thus Koster, Kasman, and SheinfeldY4 and J. SproullY5 each reviewed in 1936 a large number of recorded cases, the former 126 and the latter 132, including not only the more recent and carefully observed examples, but also the older and less certain forms of granuloma. In these papers it is claimed that Crohn's disease may be found anywhere from the jejunum to the sigmoid colon, involving either long or short segments, and often several sections of intestine separated from each other by normal bowel. The record of T. K. DalzieP is quoted, who, in 1913, gave two instances in which almost the entire small and large bowel were affected. He called it ccchronic interstitial enteritis ".It is uncertain that these conform to the granuloma described by Crohn, and it is in our view desirable that only recent authenticated cases be included in this category. Jackson', in a recent communication, refers to 219 such instances reported in America since Crohn first gave his classical description in 1932. Jackmans, in 1934, H. SchwabacherlO in 1936, and Colbeck, Hurst and Lintott in 1 9 3 9~~~ have recorded the incidence of the condition in this country.It is our view that this is a new disease ; we do not believe that a pathological condition of such a definite nature, and so unlike any of the known diseases of the intestine, can have remained for long unrecognized in this keen and critical surgical age. When operating upon the first of the cases which form the basis of this paper, we were hardly aware of Crohn's description, and yet the pathological appearance, disclosed at operation, left us in no doubt that here was something which we had never seen before, something that was not tuberculosis, malignant disease, or ulcerative colitis, and something which for its cure required radical treatment. The picture was very striking and unforgettable ; the thick, solid loop of intestine with fat standing out predominantly ; even more, the heavy infiltrated mesentery, red and edematous, with swollen glands massed within its thickened substance.