To investigate long-term survival after operation for primary hyperparathyroidism, a follow-up study was performed on 896 consecutive patients in whom this diagnosis had been clinically and microscopically verified. These patients were operated on in the years 1953-1982. Their mean age at operation was 57.3 years [standard deviation (SD) 13.1], overall cure rate was 97.0%, and postoperative mortality was 0.89%. Follow-up was 99.8% complete by the end of 1986. Mean follow-up time was 12.9 years (SD: 6.1). Two-hundred ninety-four patients were deceased, which was 118 more than in a control group (p less than 0.001). The latter was based on Swedish population statistics, matched for age, sex, and calendar year. Each year, the control group was the same size as the hyperparathyroid population. The risk of premature death remained increased (p less than 0.001) even after exclusion of poor-risk patients having their hyperparathyroidism diagnosed when being treated or followed because of other serious diseases. The main causes of premature death for the hyperparathyroid patients were cardiovascular and malignant diseases. Both occurred more often than in the control group (p less than 0.001). The results demonstrate that primary hyperparathyroidism causes damage that is not reversed by surgery.