The clinical and pathological features of human intestinal spirochetosis (HIS) are not well known. Here we report 55 patients with HIS who were diagnosed at our institution during the past 5 years. Seven patients presented with symptoms such as abdominal pain or diarrhea, while the others were incidentally diagnosed during screening colonoscopy. Most patients had non-specific endoscopic findings, including intestinal edema or erosion. The diagnosis of HIS was histologically confirmed via hematoxylin and eosin staining, periodic acid-Schiff staining, and/or immunohistochemistry using anti-Treponema pallidum antibody. Among the 55 patients, five were diagnosed with diseases other than HIS (amoebic colitis, three;ulcerative colitis, one). Sixteen patients were treated with either amoxicillin or metronidazole;only metronidazole proved to be effective. The clinical significance of asymptomatic HIS remains unknown. Some case reports suggest a risk for increased severity in patients with immunodeficiency and/or sexually transmitted diseases. Therefore, aggressive treatment for HIS should be considered, particularly in high-risk patients.