The anatomic course and variation of the thyroid veins used for retrograde thyroid phlebography were studied in 70 post mortem thyroid phlebograms. Comparison with pathological and anatomical findings showed good agreement in benign diseases of the thyroid with lesions of more than 1 cm. Infiltrating malignant changes could not be delineated with certainty and a post mortem proven parathyroid adenoma was also missed. The practical clinical significance of thyroid phlebography is therefore confined to the localisation of parathyroid tumours in primary hyperparathyroidism by selective parathoromone measurements.