This paper reports two relatively rare cases of primary carcinoid tumors of the thymus experienced by the authors. One case is a 43-year old male who presented the Zollinger-Ellison (ZE) syndrome and received total gastrectomy and distal pancreatectomy. Mediastinal tumor was found one year and seven months post operatively, for which total extirpation was performed followed by irradiation. The histological diagnosis was primary carcinoid of the thymus. The other case is a 63-year old female, who under the diagnosis of thymus carcinoid received total removal of the tumor with postoperative irradiation in 1978. In 1984, the case developed localized recurrence of the tumor, for which excision was performed again and irradiation was repeated.