The electroencephalographic, electrocardiographic, and clinical effects of carotid sinus stimulation, unilaterally and bilaterally, were studied in 122 individuals.In every case in whom satisfactory carotid sinus compression was performed cardiac slowing or asystole was obtained immediately. One-fourth of the cases showed asystoles, usually 3-5 seconds in duration but varying up to 9 seconds.In 66% of the cases high voltage 3 per second slow waves appeared abruptly in the EEG diffusely and symmetrically, after 10 seconds of sustained forceful compression of the carotid sinuses.In 6o% of the cases unconsciousness with a short tonic-clonic seizure occurred immediately after the appearance of the slow-wave discharge. The seizure lasted 5-15 seconds, with recovery immediate and complete.These effects of compression could be repeated many times with remarkable consistency without any cumulative or permanent effects upon the EEG or EKG.Compression of the common carotid arteries below the bifurcation produced immediate acceleration of the heart. The central effects were obtained after approximately 10 seconds of sustained compression and were similar to those obtained by carotid sinus compression.Elevation of blood pressure reduces the central effect of carotid sinus compression. Electric shock and prefrontal lobotomy facilitate the central effect of carotid sinus compression.The central effects of carotid sinus compression described above are thought to be due largely to interference with the carotid circulation to the brain.Abstract Teaser