Thymectomy and removal of the hyperplastic thymus have been performed in 21 patients with myasthenia. In 14 patients, thymectomy is performed through thoracoscopic access (TA), while in 7 cases through thoracotomic access (TT). The serum levels of antibodies to acetylcholine receptors (AChR) determined before and after surgery were increased in both groups of patients. Thus, thymectomy, regardless of the degree of clinical improvement in early post operative period, significantly increases the level of anti-AChR antibodies in the serum of patients in the early postoperative period compared to baseline. These changes may reflect the immune response to a stressful situation related to the traumatic surgery. It should be noted that the level of anti-AChR antibodies was significantly higher in a group of TT that may be related with a larger volume of the removed tissue.