We describe a premenopausal white woman with symptomatic acute primary hyperparathyroidism and marked osteoporosis. After undergoing a parathyroidectomy, the patient experienced not only rapid symptomatic relief, but also marked improvement in bone mineral density, which increased by 25% in the hip and by 22% in the lumbar spine 1 year after the surgery. Acute primary hyperparathyroidism should be considered in any patient with severe symptomatic hypercalcemia. Appropriate treatment with early parathyroidectomy can result in significant and rapid improvement in bone mineral density.