Carotid sinus hyperaesthesia (CSH) was found in 605 of the clinical cases observed by the authors in a 6-year period. In the patients with CSH, disorders of impulse formation and conduction, both at rest and in response to the carotid compression test, were prevalent. No relationship was demonstrable between the duration of carotid compression and the consequent rhythm disorders. Nor did the vascular state of the CSH patients affect the type, duration or severity of arrhythmia elicited by carotid compression. In 8 cases of CSH unilateral carotid sinus infiltration with lidocain was performed with the objective of pharmacological denervation. Predominance of sympathicotonia induced in this manner was not found to be provocative of arrhythmia. Sensitization of the carotid sinus reflex in response to i.v. administration of 0.5 mg digoxin was confirmed on the evidence of clinical investigations.The results thus obtained are primarily attributed to a decreased sympathetic efferentation.