The operative management of coexisting thyroid and parathyroid disease. Three hundred eight patients who underwent operation for hyperparathyroidism were studied. Fifty-two (17%) were identified who had a concomitant thyroid nodule. All 52 underwent parathyroidectomy and thyroid resection in a single operation. Eleven of these patients (21% of those with a thyroid nodule) had differentiated thyroid cancer. One patient with parathyroid hyperplasia developed permanent hypocalcemia. None had permanent vocal cord paralysis and none required tracheostomy. Thorough visual inspection and palpation of the entire thyroid gland should be performed during operations for hyperparathyroidism. Incidentally discovered thyroid nodules should prompt formal lobectomy with frozen section diagnosis; unanticipated thyroid malignancies should then be treated as independent entities. Treating simultaneous hyperparathyroidism and nodular thyroid disease with a single operation can be done safely; it avoids the expense and risk associated with neck reexploration and can detect unsuspected cancers. 