A retrospective study was undertaken to evaluate the current-day role of the plain abdominal radiograph in the diagnosis of acute appendicitis. Although there was good correlation between the number of positive abdominal X rays and patients found to have more severe changes such as gangrene or perforation, a significant number of individuals with less severe inflammatory changes of the appendix had normal X rays. Some patients subsequently found to have a normal appendix at surgery had positive findings on abdominal X ray. It appears that the abdominal X ray is not sufficiently sensitive or specific in helping to diagnose acute appendicitis in its earlier stages and in most cases can probably be eliminated from the work-up.Patients were placed into one of the following four groups according to the severity of the inflammatory process subsequently found at surgery and pathology: (1) normal appendix, (2) pathological changes of acute appendicitis, (3) findings consistent with acute appendicitis as well as inflammatory changes in the peri-appendiceal tissues and (4) severe involvement consisting of gangrenous changes in the appendix with or without perforation (table I). Abdominal X rays were analyzed for the presence of abnormal findings listed in table II.