AIM: Postoperative hematoma is a complications of thyroid surgery uncommon but potentially life threatening. It has implications for the trend toward outpatient procedures. METHODS: Retrospective review of 1.221 thyroidectomies performed at our institution over a 6-years period, to identify patients with hematomas requiring reoperation. Symptoms, treatment and findings at reoperation were evaluated. A control group (n=120) was compared for perioperative risk factors and outcome. RESULTS: Eighteen patients (1.5%) developed a postoperative hematoma. Symptoms included neck pain/pressure in 10 patients, respiratory distress in 9, wound drainage in 2, dysphagia in 1, agitation and sweating in 1. Mean time to symptom onset was 12 hours (range: 1.3-40 hours). Six hematomas presented between 7 and 24 hours, and 3 beyond 24 hours. Six patients required bedside hematoma evacuation. The bleeding source was identified in 15 patients. All patients recovered well, but one required a temporary tracheostomy. Case/controls comparison yielded in the study group a higher prevalence of hyperthyroidism (55.6% vs 25.8%, P=0.022) and intrathoracic goiter (50% vs 22.5%, P=0.029), and a longer mean hospital stay (5.22 vs 4.1, P=0.012); morbidity was not increased. CONCLUSIONS: Postoperative hematoma is an uncommon complication of thyroid surgery. If treated promptly, serious consequences can be avoided. The relatively long interval between the initial operation and the hematoma development needs to be considered when establishing outpatient practice guidelines.