In a group of 304 myasthenic patients 15 cases with thyropathies were reported: nine with hiperthyroidism, one with hypothyroidism and five with nontoxic goiter. Four patients presented diffuse simple goiter and one a multinodular goiter with normal thyroid function. No patient came from an endemic goiter region, not even familial goiter. The prevalence and influence of hyperthyroidism on myasthenic symptomatology were studied. Our findings suggest that there is no clinical correlation between both myasthenia symptomatology and thyroid dysfunction, neither significant influence on myasthenic symptoms when the endocrine disorders improve.