No Class I studies of the effectiveness of thymectomy for myasthenia gravis (MG) have been performed. Most Class II studies comparing outcomes in MG patients with and without thymectomy demonstrated higher MG remission and improvement rates in patients undergoing thymectomy. However, these Class II studies were also consistently confounded by important differences between MG patients in surgical and nonsurgical groups. Myasthenia gravis patients undergoing thymectomy were younger, more often women and were more likely to have severe myasthenia. The authors of this paper cannot determine from these Class II studies whether the observed association between thymectomy and improved MG outcomes was a result of a thymectomy benefit or was merely a result of the multiple differences in baseline characteristics between the surgical and nonsurgical groups. The authors concluded that the benefit of thymectomy in non-thymomatous autoimmune MG has not been conclusively established. Thus, for patients with non-thymomatous autoimmune myasthenia gravis, thymectomy should only be considered an option to increase the probability of remission or improvement. The quality standards subcommittee of the American Academy of Neurology recently adopted this position.