This analysis of 21 cases of ulcerative and granulomatous colitis once again points out the overlapping patterns of the 2 pathologic processes. Data indicated that ulcerative colitis was diagnosed correctly more often than granulomatous colitis at this institution. The reliability of the various "classical findings" used as criteria at this institution may be questioned, since many such findings are apparently responsible for incorrect as well as correct diagnoses. Inter-observer variation may well represent individual bias in this study; it was wide enough however to pinpoint the equivocal nature of some of the findings. The intra-observer variation (when the first reading of 18 sets of roentgenograms was compared with a second reading made 3 months later) was also substantial enough (11 to 44 per cent) to raise doubts about the possibility of achieving correct diagnosis strictly from barium enema examination. The findings in this study stress once again the necessity for basing diagnosis of a case of colitis on all its current and previous clinical roentgenographic and pathological data.5 Even when all of this information is available, instances may occasionally arise in which definite diagnosis is in doubt or in which a previous diagnosis must be reevaluated. Although most cases of ulcerative colitis and granulomatous colitis retain their roentgenographic characteristics throughout the course of the disease, there are sometimes situations in which one roentgenographic pattern evolves to another over an unpredictable period of time. A study similar to this but using histologic material and highly trained pathologists should be interesting and would contribute further to the understanding of the set of conditions surrounding granulomatous and ulcerative colitis.