Electric testing was performed in 106 myasthenia gravis patients before and after transcervical thymectomy. Twenty-nine were followed for 3 to 24 months. Results were correlated with thymic pathology, duration of disease, age at operation, and follow-up clinical status. Electric improvement was significantly greater in patients without thymic germinal centers or with only rare to occasional germinal centers, in patients operated on within 1 year after onset of symptoms, and in patients under age 30. Electric improvement immediately after thymectomy heralded later clinical improvement in those patients without germinal centers or with rare to occasional germinal centers. Electric-clinical correlations were excellent in patients with longer follow-up. Serial electric testing provides an objective evaluation of the patients' clinical status post-thymectomy.