Thrombosis of the left subclavian vein occurred in a 44-year-old man. It was found to be caused by an atypical thymus carcinoid of the anterior mediastinum without carcinoid syndrome. Primary resection was not possible, but it was removed after three cycles of neoadjuvant chemotherapy with doxorubicin, cisplatin, vincristine and cyclophosphamide. Increased concentrations of alkaline phosphatase and parathormone were then noted. Subtotal parathyroidectomy revealed hyperplastic parathyroids. A gastrinoma was suspected from a history of peptic ulcer for many years which had persisted despite a Billroth II gastric resection 10 years ago. Serum gastrin, analysis of gastric secretion and a secretin-stimulating test confirmed the diagnosis. Recurrent episodes of weakness and syncope, in the presence of low blood sugar levels and a positive C-peptide suppression test, were interpreted as due to an insulinoma. There was no evidence of increased hypophyseal or adrenal function. Finally, in the absence of a family history, multiple endocrine neoplasia type 1 (MEN 1) was diagnosed with co-existing primary hyperparathyroidism, gastrinoma, insulinoma and thymus carcinoid. Somatostatin-receptor scintigraphy provided localization of the MEN 1 with enrichment in the thorax and abdomen.