Case report of a 27 years old male with myasthenia in which there was a marked disturbance of swollowing. Etiology was not discovered. Neurological examination was negative, excepting the muscular asthenia. General clinical examination was negative. There were no signs of thymus pathology. Electric examination revealed a negative Jolly reaction. Improvement followed treatment with prostigmine combined with ephedrine sulfate in daily dosages of 0.05 centigrams.