Association between primary hyperparathyroidism and Paget's disease of bone is extremely uncommon, despite the relatively high incidence of both entities. The mechanism of this association remains unknown. Dramatic changes in parathyroid function are found in patients with Paget's disease and, on the other hand, the evolution of Paget's disease is influenced by parathyroid functional disorders. We reviewed 175 patients with Paget's disease and 60 with primary hyperparathyroidism, followed during 10 years. We only found 5 cases with the association of the two diseases. Approximately equal number were male and female (ratio: 1.5/1) patients and the average age was 63.60 +/- 2.65 years. Hypercalcemia in Paget's patients, and in increase in alkaline phosphatase in post parathyroid adenoma surgery patients were the clues that suggested the presence of the second disease. Surgical treatment was indicated in 3 patients, and the others were treated with antiresorptive drugs. We also reviewed the cases published since 1934, comparing their diagnostic, clinical, treatment and evolution features with our own cases.