A case of submucous lipoma of the transverse colon is reported. The patient, a man aged 61, complained of recurrent crampy periumbilical pain. A plain x-ray of the abdomen was negative, while a barium enema showed an intramural filling defect of the transverse colon which was interpreted as a probably degenerated colonic polyp. Laparotomy did not clarify the diagnosis which was readily clear when the lesion was cut, and confirmed by histology.