PURPOSE: Neck surgery is one of the newest fields of endoscopic surgical application. We have developed a technique for performing endoscopic thyroidectomy using a breast approach and low-pressure CO2. We report this surgical procedure and its results. METHODS: One hundred patients underwent endoscopic thyroidectomy using a breast approach. Preoperative fine needle aspiration cytology revealed 74 benign nodules, 21 follicular neoplasms, 4 in which there was difficulty in distinguishing between benign and malignant tumor and 1 not checked. We used 3 incisions on both upper circumareolar areas and one at about 3 cm below the clavicle on the tumor side. Three trocars, 5 mm, 10 mm, 15 mm were used. Subplatysmal and subcutaneous operative space was created with CO2 insufflation at 6 mmHg of pressure. The thyroidal vessels and the parenchyme of the gland were dissected and divided with an ultrasonically activated scalpel and commonly used laparoscopic instruments. RESULTS: The subjects were 93 women and 7 men with ages ranging from 7 to 63 years (mean 38.9 yerars). The operation time 136+/-9.85 minutes before year 2000 and 66.8+/-8.26 at year 2000. There were 6 cases of conversion to conventional thyroidectomy, 1 case of uncontrolled intraoperative bleeding, 1 case of invasive follicular carcinoma and 4 papillary carcinoma. Postoperative complications occurred in 5 cases; 1 case of permanent recurrent laryngeal nerve palsy, 3 cases of transient voice change and 1 case of severe chest discomfort for 3 months. There was no occurrence of subcutaneous emphysema. The average of postoperative hospitalization time was 4.5+/-0.35 days. Operative scars were completley concealed by clothes and the patients were satisfied with the cosmetic result. CONCLUSION: This approach completely avoided operative scars in the neck and resulted in satisfactory cosmetic result with minimal scars in the breast. We believe that endoscopic thyroidectomy using breast approach is feasible and safe for resection of thyroid tumors.