The effect of bilateral truncal ligation of the inferior thyroid artery on parathyroid function is prospectively analyzed in two homogeneous groups of 10 patients treated by total thyroidectomy, with (G1) and without (G2) truncal ligation, comparing immediately postoperative and late serum calcium levels. A significant decrease in mean calcemic levels (minimal ones 2.1, with n.v. 2.1-2.6 mmol/l) was observed in both groups no longer than in the first postoperative days. There was no significant difference in global (clinical + laboratory) hypocalcemia rate (G1 = 0-30% vs G2 = 10-40% respectively); nevertheless hypocalcemia was noted paradoxically to occur more frequently in G-2 patients, out of which one developed a permanent hypoparathyroidism.