Objective To determine whether the clinical and pathologic characteristics and prognoses of myasthenia gravis (MG) patients below 15 years differ from those patients over 50 years after thymectomy. Methods We reviewed the registry material of 30 pediatric and 32 elderly MG patients after thymectomy,including their age,sex,clinical classification,pathological types,and prognoses. The Chi-square test or Wilcoxon’s rank-sum test was used to determine the statistical differences between the children and elderly groups.Results No significant difference was seen in sex distribution between the two groups (Chi-square test, P =0.625),but there were differences in clinical classification: more type Ⅰ was observed in the pediatric group than in the elderly group,but more type Ⅱor Ⅲ was seen in the elderly group (Wilcoxon’s rank-sum test,P <0.001). As to pathological types,the pediatric group was also significantly different from the elderly group (Chi-square test,P <0.01). All of the patients (100%) in the pediatric group had thymus hyperplasia,but in the elderly group more than half (56.26%) were found to have thymoma (benign or malignant). The prognoses after thymectomy were better in the pediatric group than in the elderly group (Wilcoxon’s rank-sum test,P <0.001). Conclusions Because the prognoses are generally better than those of the elderly patients,we should be careful when operating on pediatric patients of ocular type. The elderly patients tend to receive more aggressive treatment because of more severe generalized types often associated with thymoma and poor prognoses. Both pediatric and elderly patients are seldom associated with other autoimmune disease. Objective To determine whether the clinical and pathologic characteristics and prognoses of myasthenia gravis (MG) patients below 15 years differ from those patients over 50 years after thymectomy. Methods We reviewed the registry material of 30 pediatric and 32 elderly MG patients after thymectomy, including age, sex, clinical classification, pathological types, and prognoses. The Chi-square test or Wilcoxon’s rank-sum test was used to determine the statistical differences between the children and elderly groups. Results No significant difference was seen in sex distribution between the two groups (Chi-square test, P = 0.625), but there were differences in clinical classification: more type I was observed in the pediatric group than in the elderly group, but more type II or III was seen in the elderly group (Wilcoxon’s rank- sum test, P <0.001). As to pathological types, the pediatric group was also significantly different from the elderly group (Chi-square test, P <0.01). All of the p atopic (100%) in the pediatric group had thymus hyperplasia, but in the elderly group more than half (56.26%) were found to have thymoma (benign or malignant). The prognoses after thymectomy were better in the pediatric group than in the elderly group (Wilcoxon’s rank-sum test, P <0.001). Conclusions Because the prognoses are generally better than those of the elderly patients, we should be careful when operating on pediatric patients of ocular type. The elderly patients tend to receive more aggressive treatment because of more severe generalized types often associated with thymoma and poor prognoses. Both pediatric and elderly patients are seldom associated with other autoimmune disease.