A 61-year-old Bristish woman, had history of visiting Far East for years, presented with abdominal cramping pain and bloody mucous diarrhea for 3 weeks. Examination of her stool showed that it contained white and red blood cells more than 100 cells/mm3 and that her stool culture was negative for enteropathogenic organisms. A colonoscopy was performed to exclude malignancy, ulcerative colitis, or infectious colitis. The colonoscopy revealed the presence of numerous well-circumscribed, oval shaped ulcers, size 0.2-1.0cm spanning the area from her cecum (Figure A) to her rectum (Figure B). Tissue pathology revealed the presence of amebic trophozoites containing digested red blood cells (Figure C). The patient was successfully treated with metronidazole. Diffuse colonic ulcers (Figures A) and (B) may result from several different causes, such as amebiasis, tuberculous colitis, ulcerative colitis, or malignancy. These conditions can be differentiated by performing colonosopic and pathological studies.