A Japanese Black bull aged 20 years died following progressive loss of the body weight. Pathological examination disclosed multiple endocrine tumors including thyroid C cell carcinoma with metastases to the cervical lymph nodes and lung, adrenal pheochromocytoma and pituitary chromophobe adenoma in the pars distalis. The serum calcium content was as midly low as 8.0 mg/d/ at the terminal stage. The bull had daily ingested the ration containing 1.9 times the recommended calcium amount for 8 years and 120,000 units of vitamin D(3) for 5 years prior to death. The long-term dietary intake of moderately excessive calcium With vitamin D(3) might be related to the pathogenesis of the thyroid C cell carcinoma.