Twenty-four 10-day-old, artificially reared, coccidia-free goslings (Anser cygnoides var. domestica) were inoculated orally with 1.0×10⁵–1.0×10⁶ sporulated oocysts of Eimeria nocens, and killed at intervals from 30 to 336 hr postinoculation (PI). Parts of the visceral organs, including intestines, kidney, liver, gallbladder, and spleen from inoculated goslings, were fixed and sectioned. The life cycle of E. nocens and histologic changes during infection were examined microscopically. The results showed that at least 3 generations of meronts developed in the endogenous stage of the life cycle of E. nocens. Two types of meronts were found. The first completed maturation at 54 to 78 hr PI. These meronts were the first generation, with each forming about 12 merozoites. The second completed maturation at 102 to 240 hr PI. These meronts were the second or third generations, with each meront forming about 24 merozoites. Development of gamonts began at about 198 hr after infection. The prepatent period was 9 days and discharge of oocysts continued for 4 days. Sporulation of oocysts occurred in 60–72 hr at 25 C. Eimeria nocens invaded the posterior jejunum, ileum, caecum, rectum, and cloaca. Developmental stages were localized within the epithelial cells of villi and crypts, and in lamina propria. Marked histological changes, including desquamation and necrosis of intestinal epithelium, submucosal edema, hemorrhages, infiltration of inflammatory cells, and villous atrophy, were seen during the periods of late merogony, gamogony, and oocyst shedding. They were most pronounced in the ileum and the regions nearby. The infected goslings showed severe diarrhea, bloody feces, anorexia, emaciation, and even death, suggesting that E. nocens is highly pathogenic for goslings.