PRIOR to Virchow's classic description r of mucocele, in 1863, when he considered it a “colloid degeneration” of the appendix, Rokitansky, in 1842, described it under the term “hydrops of the appendix.” Later, in 1864 and 1888, Cruveilhier and Werth reported the chief complication of the disease as a “gelatinous degeneration of the peritoneum” and as “pseudomyxoma peritonei,” respectively. These free and encysted gelatinous masses in the peritoneum, however, are much more common in the female secondary to rupture of pseudomucinous cysts of the ovary and occur only in the male following rupture of a distended mucocele of the appendix. Frankel, in 1901, reported the first case of pseudomyxoma peritonei, with ruptured appendix, containing the same gelatinous substance. Original clinical observations on mucoceles reported by Maydl and Lennander, in 1892 and 1893, respectively, make no mention of autopsy or operative proofs. Numerous case reports by Stengel, Nash, Porter, Deaver, Simon, and others add little to the symptomatology and practically nothing by way of diagnostic criteria. This fact, plus the rarity of this condition, accounts for the low incidence of correct pre-operative diagnosis. Mayo and Fauster, in a review of surgical cases at the Mayo Clinic, 1917 to 1930, inclusive, in 31,200 cases of appendectomy, encountered mucocele of the appendix 76 times—an incidence of 0.24 per cent. Since Virchow's description, approximately 250 cases have been reported. The clinical diagnosis of mucocele of the appendix is extremely difficult owing to the lack of any constant pathognomonic signs or symptoms. The patient may experience vague abdominal discomfort, pains, and tenderness in the lower right quadrant for many months and not until the pain becomes quite distressing or the tenderness over the appendiceal region markedly intensified is medical relief sought. At this time a palpable tumor mass may be encountered in the lower right quadrant. There may be referred somatic pain or deep splanchnic pain in the region of the appendix, due to tension on the mesentery. Occasionally, as in the recent case of Heatley (1), the patient may present signs and symptoms of an acute surgical condition with fever and leukocytosis as the result of torsion of the proximal appendix incident to rotation of the mucocele; this results in intraluminal and interstitial hemorrhage and gangrene. The use of x-ray in investigation of mucocele of the appendix has been considered limited, due to the fact that the proximal lumen of the appendix is almost invariably completely stenosed, thus prohibiting the entrance of any of the opaque medium; also, because of failure to elicit signs of extrinsic pressure on the bariurnfilled cecum. Rarely is there patency of the proximal end to permit passage of the barium and allow for full visualization of the entire mucocele, as in the case reported by Vorhaus.