In order to explain the pathogenesis of pulmonary pathology in myotonic dystrophy, the mechanism of deglutition was examined in 44 patients. In 43, severe impairment of deglutition and prolonged retention of contrast material in the recesses of the pharynx were found. Clearance time was not connected with the age of the patient, the duration of the disease, or the severity of myotony; but the highest values were found in the most severe cases. Impairment of deglutition and retention of various materials in the pharynx seem to be among the most constant signs of myotonic dystrophy. In 12 patients contrast material was repeatedly spilled into the bronchial tree. In 2 cases aspiration of milk was observed on ear, nose and throat examination. This phenomenon of aspiration is probably caused by an inadequate closing of the vocal cords due to the involvement of laryngeal and pharyngeal muscles in a pathologic process. It seems that this mechanism explains the pathogenesis of repeated pulmonary infections and the development of chronic lung diseases in myotonic patients. Treatment with steroids, quinine, or procaine amide did not change the clearance time or the appearance of aspiration.