Over a period of 3 months a 51-year-old woman developed a depressive syndrome with loss of memory, inability to find words, impaired fine movements and phases of spacial disorientation. Biochemical tests demonstrated occasional slight rises in serum calcium (2.8-2.9 mmol/l) and parathormone (4.6-5.2 pmol/l). She had a grade II nodular goitre with normal thyroid function. Ultrasonography of the thyroid suggested a right cranial parathyroid adenoma, confirmed at a right thyroidectomy with resection of the right upper parathyroid, while the other parathyroid glands were grossly normal. Calcium and parathormone levels returned to normal after the operation, as did the neuropsychiatric symptoms (within two months). This typical case illustrates that even in seemingly isolated neuropsychiatric changes an organic disease, like primary hyperparathyroidism, needs to be thought of.