Purpose: During the past decade, various techniques of endoscopic thyroid surgery have been introduced. We have developed a novel method of gasless endoscopic thyroidectomy via an axillary approach. The present report describes the technique of this method, and analyzes its surgical outcome. Patients and Methods: Between Nov. 2001 and Dec. 2007 (actual operation period was 50 months), 581 patients with thyroid tumors underwent gasless endoscopic thyroidectomy via an axillary approach. The clinical and pathologic characteristics of patients, operation type, operation time, post operative hospital stay and post operative complications were analyzed retrospectively. Results: Among the 581 patients, 171 patients had benign tumor and 410 patients had malignant tumor. There was no conversion to open surgery. The operating time and the length of post-operative hospital stay were 129.4±51.3 minutes, 3.3±1.7 days in benign tumor, and 135.5±47 minutes, 3.4±0.9 days in malignant tumors, respectively. The tumor size was 2.7±1.2 cm in benign tumor and 0.78±0.5 cm in malignancy. Central compartment lymph node metastasis was found in 112 (27.3%) patients and lateral neck lymph node metastasis in 13 (3.1%) patients. As post-operative complications, transient hypocalcemia occurred in 19 patients and transient hoarseness was in 13 patients and permanent vocal cord palsy occurred in 2 patients. In the TNM stage, 366 (89.2%) patients were stage I, 43 (10.5%) patients were stage III and 1 (0.2%) patient was stage IVA. Conclusion: According to our experience, gasless endoscopic thyroidectomy using a trans-axillary approach is a feasible and safe method. Endoscopic thyroid surgery has become a new treatment modality for the patients with benign tumors and can be an effective alternative treatment for the selected patients with thyroid cancer.