Hemorrhage is a complication of thyroid surgery less important than recurrent laryngeal nerve injury or hypoparathyroidism, but extremely dangerous. Hemorrhage may be early or delayed. Early hemorrhage occurs generally in the operating theatre and is made easier by vomiting and coughing after removal of the tracheal tube. For this reason it is indispensable for the surgeon to remain until the patient is awake and carefully control the drainages. Delayed hemorrhage generally occurs some hours after the surgical operation with a swelling of the neck associated with difficulties in the breathing, due to tracheal compression. In our institution, from 1988 to 1992, we performed 1800 surgical operations for thyroid diseases and we observed 9 early hemorrhages and 10 delayed hemorrhages. In all cases we performed reoperation in general anaesthesia. In our series the hemorrhage was due to the vessels of the pre-thyroidal muscles and of the inferior pole, rarely of the superior pole. We had no complications after the reoperation. To prevent this complication, we have to respect some technical aspects: accuracy in the ligature of the blood vessels of the superior and inferior pole; partial section of the pre-thyroidal muscles; to bring the remaining thyroid (in case of subtotal thyroidectomy) near to the trachea with some stitches.