Myasthenia gravis (MG) is a known potentially debilitating, and life threatening disease, for which thy-mectomy is considered the optimal treatment. Ten to twenty percent of patients are found to have thymomas, which reflects its presence in a differ­ent clinical presentation, more severe disease state and worse response to surgery. The aim of this study is to compare between thymomatous and nonthymomatous MG. The study in­cluded 63 patients of myasthenai gra­vis for whom thymectomy was per­formed. They were divided into two groups, Group 1 of 51 patients with nonthymomatous MG, and Group 2 of 12 patients with thymomatous MG. The mean age of group 1 was 27.6 years while that for group 2 was 48.3 years (P.value 0.003). The female to male ratio in group 1 was 2.9:1 and
that of group 2 was 1:2 (P.value 0.001). There was no difference in the symptomatology or duration of illness between the two groups. Group 2 pa­tients needed more medications than those of group 1 (P.value 0.01).Group 1 patients were mainly in a moderate­ly severe disease grade (mainly grade IIA , IIB , and III) while those of group 2 were in an advanced disease grade (IIB, III, and IV) (P.value 0.001).Extended thymectomy was performed for ail the patients with good prognosis in group 1 patients (51% remission , 45.1% benefited, and 3.9% unchanged ) and worse prognosis in group 2 patients (no re­mission, 50% benefited, and 50% un­changed or worse) (P.value 0.001). We concluded that thymomatous MG is markedly different from nonthy­momatous MG with older age presen­tation, more in men , appears in an