The purpose of this paper is again to remind the radiologist to be “coprolith-conscious.” Coproliths were not diagnosed in our department before 1949. In the first five years after we had become “coprolith” conscious, however, 42 cases were seen, of which 35 were diagnosed preoperatively and 8 postoperatively because the surgeon requested an x-ray study of the removed appendix. This report will be limited to the cases with a preoperative diagnosis. The word “coprolith” is derived from the Greek, meaning “dung stone.” It is used, according to the suggestion of Thomas (1), to emphasize the radiopacity of the concretion and thus distinguish fecaliths which are visible roentgenographically from others frequently found in the appendix. In his study of a large series of fecaliths, only 25 per cent contained enough calcium to be visualized on an abdominal film. The first mention of appendiceal stone was made in 1813 by Wegeler (2). The first report of a correct preoperative x-ray diagnosis was that of Weisflog (3) in 1906. Seelig (4) in 1908 introduced the term “coprolith” and was the first to describe this condition in the American literature. Since that time, there has been a multitude of reports. An extensive review of the literature is unnecessary in view of the excellent analyses of Felson and Bernhard (5) and Laforet et al. (6), in 1947 and 1951, respectively. The mechanism of coprolith development proposed by Kelly and Hurdon (7) in 1905 is the most widely accepted. They propose that impairment of the normal peristaltic return of fecal content from the appendix results in inspissation. Subsequent irritation and accompanying bacterial activity due to the fecal mass cause a low-grade inflammation with mucus secretion. The inorganic salts, mainly calcium phosphate, contained in the mucus are precipitated on the surface of the fecal nucleus, producing an increase in size. Wangensteen and Bowers (8) suggest that the appendix frequently behaves as a closed loop in relation to the intestinal canal, permitting entry but preventing free extrusion of the fecal stream; the coprolith is then formed in the lumen by stasis upon the fecal nucleus. These authors stress the closed loop phenomenon as the initiating factor in appendicitis and regard inflammation and suppuration as consequences of the obstruction. This explains why a patient may have a coprolith for some time before the development of acute appendicitis. Maver and Wells (9) studied the chemical composition of a number of coproliths and found the content to be as follows: material soluble in fat solvents (mainly soaps with considerable coprosterol), 50 per cent; inorganic material (mainly calcium phosphate), 25 per cent; organic residue (mainly vegetable fibers), 20 per cent. Approximately 130 cases of coproliths have been reported to date. The frequency of their occurrence as given in the literature varies considerably according to the material from which the cases are selected.