Primary hyperparathyroidism causes excessive bone resorption with a decrease in bone mineral density. Fractures of the vertebras and appendicular bones, however, seem uncommon, even in the long term. We report three patients who presented with bone insufficiency fractures as the inaugural symptom of primary hyperparathyroidism. The three patients were women, aged 62, 65 and 86 years, respectively, who presented with fractures of the medial tibial plateau, femoral neck of femoral neck and tarsus. Laboratory tests showed hypercalcemia, hypophosphatemia and elevated parathyroid hormone levels. Apart from confusion in the 86-year-old patient, there were no clinical manifestations. A bone biopsy obtained in one patient showed increased resorption parameters with no loss of bone trabecular volume; the two other patients underwent absorptiometry, which disclosed a marked decrease in bone mineral density at the spine and femoral neck. There were no risk factors for osteopenia apart from advanced age and female gender. A parathyroid adenoma was removed surgically in all three cases. Vitamin D deficiency was a concomitant abnormality that probably exacerbated the adverse effects of hyperparathyroidism on the skeleton.