BACKGROUND: Successful kidney transplantation is believed to cure secondary hyperparathyroidism, but persistent disease has emerged in a significant number of allograft recipients. A parathyroidectomy is ultimately required in some of these patients. To gain insight into the incidence, risk factors and consequences of parathyroidectomy in patients with a functioning renal graft, we performed a retrospective case-controlled study. METHODS: Charts of 1743 recipients of a kidney allograft, transplanted between 1989 and 2004, were reviewed. Patients with a functioning graft subjected to parathyroidectomy were identified. Their charts were checked for various demographic, clinical and biochemical variables. The data were compared with those obtained from patients transplanted in the same period, but not subjected to parathyroidectomy (controls). RESULTS: Persistent hyperparathyroidism in patients with a functioning graft requiring parathyroidectomy developed in 90 patients, corresponding to an overall parathyroidectomy rate of 8.89 per 1000 person-years at risk. Female gender (OR 1.79, P < 0.05) and higher pre-transplant serum concentrations of PTH (OR per 1 ng/l increase, 1.003, P < 0.0001) and calcium (OR per 1 mg/dl increase, 2.58, P < 0.0001) were identified as independent predictors of post-transplant parathyroidectomy. A significant increase of the serum creatinine was observed after parathyroidectomy (1.91 +/- 0.72 vs 1.76 +/- 0.63 mg/dl, P < 0.01). Graft survival, however, was similar in cases and controls. CONCLUSION: Persistent hyperparathyroidism requiring parathyroidectomy after successful renal transplantation is a common clinical problem. Female patients with a high pre-transplant serum level of PTH and calcium are especially at risk. Although graft function deteriorates shortly after parathyroidectomy, graft survival, overall, is not different from controls.