Clinical response to thymectomy in patients with myasthenia gravis varies in terms of timing and degree of improvement. Electrophysiological test is a reasonably reliable and objective way to evaluate neuromuscular transmission in these patients. The purpose of this study was to evaluate the electrophysiological response before and after thymectomy by repetitive nerve stimulation test in order to estimate the timing of initial improvement, progress and degree of improvement after thymectomy. According to electrophysiological findings, it appeared that neuromuscular transmission in these patients might have begun to improve even as early as one week after thymectomy and steadily improved by the end of one year of the study corresponding to clinical improvement.