PURPOSE: A post-thyroidectomy hematoma is a rare complication, affecting 0.1~2.5% of patients undergoing a thyroidectomy, but this complication deserves special attention because it is potentially life threatening and unpredictable. This study was performed to evaluate the prevalence and clinical features of post-thyroidectomy hematomas as well as their implications on the early discharge after a thyroidectomy. METHODS: In a retrospective review of 5, 465 patients that underwent a thyroidectomy between Jan 1994 and Dec 2003, 21 (0.38%) with post-thyroidectomy hematomas were identified. The clinical features and outcomes of these 21 patients were evaluated. RESULTS: The 21 patients were composed of 3 men and 18 women, with a mean age of 47.9+/-19.4 years, ranging from 23~80. The mean time to recognition of the hematoma was 7.0+/-15.3 hours, ranging from 0~72. Sixteen hematomas (76.2%) presented within 6 hours postoperatively, 4 (19.0%) between 6 and 24 hours, and 1 (4.8%) after more than 24 hours. Except for two patients with minimal hematomas, the other 19 underwent re-exploration under general anesthesia after evacuation of the hematoma at bedside. The bleeding source was the lacerated strap muscles in 16 patients (76.2%), venous in 3, arterial in 1 and thyroid lobe stump in 1. Mean hospital stay was 5.2+/-2.0 days, ranging from 2~9. There were no mortality or complications after reoperation, and patients required a blood transfusion or tracheostomy. There were no significant differences in the clinical features between Graves' disease and non-Graves' disease, as well as between benign and malignant groups. CONCLUSION: Early detection and prompt surgical intervention are critical to a successful outcome in patients with post- thyroidectomy hematomas. Because most of the patients in our series with post-thyroidectomy hematomas presented within 24 hours postoperatively, early discharge, with careful monitoring for the first 24 hours after a thyroidectomy, can be recommended. However the relatively long interval between the initial operation and the development of the hematoma should be considered when recommending early discharge after a thyroidectomy.