0 NE of the causes of spontaneous perforation of the intestinal tract Iisted by textbooks on surgery and pathoIogy is the helminth Ascaris Iumbricoides. This etioIogic agent is often onIy mentioned, and the pathogenesis of such perforation is not discussed. I wish to present for anaIysis my findings regarding the roIe of the heIrninth A. Iumbricoides during an outbreak of intestina1 perforations due to paratyphoid fever. This outbreak occurred among the North Korean prisoners of war durink the Korean conffict. This episode of 203 spontaneous perforations of the iIeum due to SaImoneIIa paratyphi has been previousIy summarized by the author [I]. Ascaris Lumbricoides. WhiIe man is the onIy known host of A. Iumbricoides, Iower animaIs harbor a number of cIoseIy reIated species. Infection is worId-wide, but predominates where sanitary and cIimatic conditions favor its dissemination. A. Iumbricoides, or the roundworm of man, is a Iarge, flesh-coIored parasite of the smaI1 intestine. The femaIes measure 20 cm. or more in Iength by 5 mm. in diameter, and the males 16 cm. by 3 mm. The eggs are underdeveIoped when passed in the feces. In soi or water they become infective in about one week; and may survive despite adverse chemica1 conditions. Ingested in food, particuIarIy raw vegetabIes or water, they hatch in the intestine. The embryos, however, do not deveIop directIy into aduIts in this site, but gain access to the circuIation where they are carried to the Iungs and escape into the air spaces. Via the trachea, they reach the pharynx and are swaIIowed. DeveIopment of the ascaris occurs during migration and is compIeted in the smaI1 intestine, where egg-producing aduIts may be found about two and a haIf months after infection. In man the aduIt A. Iumbricoides is capabIe of causing (I) anemia, (2) inflammation of the intestina1 waI1, (3) intestina1 obstruction, and (4) intestina1 perforation. AIthough the first three conditions are fairIy we11 recognized, the abiIity of the roundworm to perforate the intestina1 waI1 has Iong been a tdpic of argumentative discussion. The basic issue of such discussion is whether or not the ascaris can perforate a heaIthy intestina1 waI1, and also whether it can pass through the enteric waI1 into the free peritoneal cavity without causing a visibIe opening in the bowe1 waI1. SchuItze [2] in 1906 and KaiserIing [s] in 1922 both described an ascaris with its head buried in the intestina1 waI1 as if in the process of burrowing through. Gruber [b], GIanzmann [T] and Peiper [6] each beIieve the ascaris can perforate a healthy intestina1 waI1. Gruber attributes this abiIity to the production of a toxin which necroses the intestina1 waI1. Henoch [7], LeIong [8] and others do not beIieve the ascaris can perforate a healthy intestina1 waI1, but beIieve some other factors must first weaken and uIcerate the bowe1 waI1 before the ascaris can pass into the free peritonea1 cavity. During the Russo-Japanese War SiIberberg [9] performed autopsies on those patients who had died of intestina1 perforation, and found a11 to have typhus abdomin,aIis. Again, however, due to the presence of the roundworm free in the peritonea1 cavity, the question arose as to whether or not the roundworm had caused the weakened waI1 to perforate. As yet there has been no feasibIe expIanation of the finding of A. Iumbricoides free in the