We studied the clinical aspects of 18 patients from whom MRSA was detected from the stool and compared with 9 enterocolitis cases (7 male, 2 female, median age 72.4 y.o.) with 9 colonization cases (5 male, 4 female, median age 70.2 y.o.) from 1991 June to 1995 May. Cases of postoperative, use of anti-peptic ulcer drugs and administration of antibiotics for enterocolitis were more than that of colonization. On the other hand, eatable patients in the colonization group who could take food orally were more in number. Many patients of both enterocolitis and colonization were colonized in the respiratory tract. Drug sensitivity of MRSA in both cases were almost the same and the coagulase type were all that of II. Three courses on how MRSA enterocolitis occurs is considered. At first, colonization in the respiratory tract, second, proliferation of MRSA in the higher pH gastric juices as a result of gastrectomy or use of anti-peptic ulcer drugs, and third, selection of MRSA after administration of antibiotics.