Heart studies were carried out in 7 patients with end-stage renal disease (ESRD) who underwent parathyroidectomy for secondary hyperparathyroidism. The studies, which included echocardiography and equilibrium radionuclide angiography (ERNA), were performed prior to parathyroidectomy and 2 weeks, 3 months, and 6 months following it, on a nondialytic day. Heart rate decreased from 89.3 ± 1.3 to 81.4 ± 1.5 min-1 (p < 0.001) following parathyroidectomy and returned to the initial level at 3- and 6-month examination. Cardiac output decreased from 3170 ± 68 to 2943 ± 57 ml/min (p < 0.01) following parathyroidectomy and returned to basal level on 3- and 6-month determinations. End-diastolic dimension (EDD), end-systolic dimension (ESD), septal and posterior wall thickness and shortening fraction (SF) as measured by echocardiography were normal prior to parathyroidectomy and remained unchanged following it. Left ventricular ejection fraction (LVEF), end-diastolic and end-systolic volumes measured by ERNA did not change following parathyroidectomy. This study suggests that hyperparathyroidism has little effect on cardiac performance and, except for a short-lived decrease in heart rate and cardiac output, parathyroidectomy does not affect cardiac performance when performed in patients with preoperatively normal cardiac output.