In an analysis of myasthenia crises during the past 20 years, the incidence of crisis remained fairly constant at 12-16%, but the fatality rate of crises declined from 42% to 6%, and the overall mortality of myasthenia declined from 12% to 3.3%. Most crisis episodes were caused by aspiration pneumonia or occurred in patients with severe dysphagia, who were at risk of aspiration. Cholinergic drug therapy clearly was not useful during crisis, and should probably be discontinued while the patient is on a respirator. Fifteen of 28 patients with thymectomy had 21 episodes of crisis months or years after surgery. Ultimately, 42% of crisis survivors achieved a state of improved myasthenia or remission after one or more crises.