Three aggressive carcinoid tumors with liver metastasis arising in the duodenum (Case 1, 72-year-old man), ileum (Case 2, 72-year-old man), and rectum (Case 3, 67-year-old woman) were studied. Case 1 initially suffered from hemorrhage from an exophytic large tumor and developed a liver metastasis after operation. Cases 2 and 3 first presented as multiple liver metastases. Case 3 had a small submucosal tumor and showed a relatively high cell proliferation activity. Neoplastic cells expressed gastrin in Case 1, serotonin in Case 2, and did not express several peptides in Case 3.