Changes in blood pressure and renal function were investigated in 62 patients with primary hyperparathyroidism treated surgically, in an attempt to assess whether or not hypertension and renal impairment should be regarded as important indications for parathyroidectomy. 29% were hypertensive pre-operatively and the blood pressure remained elevated after parathyroidectomy in all of these patients. Hypertension developed for the first time after parathyroidectomy in 45% of those patients who were normotensive before surgery. Renal function was normal initially in 73% and mild renal impairment developed after surgery in 9% of these patients. At the end of the follow-up period, the prevalence of hypertension was higher in patients with renal impairment pre-operatively (88%) than in those with normal renal function (51%). We conclude that hypertension alone should not be regarded as an indication for parathyroidectomy in asymptomatic hyperparathyroidism. No firm conclusions can be reached about the importance of mild renal failure as an indication for surgery and the question is unlikely to be resolved without conducting a prospective controlled trial.