SUMMARY1. Twenty cases of hypernephroma metastasising to the thyroid have been collected and one has been added.2. An account of this case which had misleading features is given.3. In all cases of growths exhibiting unusual features a carcinoma of the kidney should be excluded.My thanks are due to Sir Cecil Wakeley for permission to publish the clinical details of this case and for his encouragement, to Professor H. A. Magnus for the use of the pathological reports and helpful advice, to Dr J. Blewett for permission to reproduce the radiological findings, and to Mr Smith for the photographs.