After successful subtotal parathyroidectomy (PTX) in 10 chronic haemodialysis patients, significant elevation of Epo was observed, from 48.4 +/- 17.8 mU/ml(M +/- SEM) at preoperative state to 103.3 +/- 34.7 mU/ml at 6 h and 163.4 +/- 50.2 mU/ml at 12 h after PTX. Significant reductions in both PTH-m and ionized calcium (iCa) were confirmed. Since Epo did not increase in the cases with an inadequate PTX and ovariectomy, an abrupt reduction in PTH with a decrease in iCa may play some role in the elevation of Epo.