A 44-year-old man has been seen by the present authors, apparently the third reported case of triceps brachii rupture. He had had bilateral nephrectomies one year earlier and since then has been medicated with Dilantin for grand mal seizures which followed hypovolemia during dialysis. A grand mal seizure immediately preceded the patient's right triceps brachii rupture and other multiple orthopaedic injuries. Following repair of the tendon defect the patient regained an active range of motion. The possible relationship of tendon rupture and avulsion to primary and secondary hyperparathyroidism is discussed.