Intestinal coccidiosis in a 6-mo-old infant terminated fatally after 30 wk of continuous total parenteral nutrition, and proved refractory to treatment with antibiotics, hydrocortisone, and antimetabolic agents. Intestinal biopsies obtained at laparotomy revealed flattened mucosa infiltrated with coccidia at various stages of the parasites' life cycle. The course was characterized by severe diarrhea due to a cholera-like hypersecretion of intraluminal fluid. This case suggests that intestinal coccidiosis may be included among the small number of conditions responsible for authentic "intractable diarrhea of infancy."