This study determines the results of programmed stimulation in patients with syncope or near-syncope presumed to have the carotid sinus syndrome based on the finding of carotid sinus hypersensitivity and the absence of any other apparent cause for syncope or near-syncope after clinical evaluation. Fourteen patients had coronary artery disease, 1 had dilated cardiomyopathy and 18 patients did not have structural heart disease. Programmed simulation was performed at 2 basic drive cycle lengths and 2 right ventricular sites with 1 to 3 extrastimuli. Sustained unimorphic ventricular tachycardia (VT) was induced in 5 of 15 patients who had structural heart disease, and in none of the 18 patients who did not (p less than 0.05). Polymorphic VT or ventricular fibrillation (VF) was induced in 5 of 15 patients (33%) who had structural heart disease, and in 5 of 18 patients (27%) who did not (p greater than 0.05). Patients who had inducible unimorphic VT were treated with antiarrhythmic drugs that suppressed the induction of VT, and 4 of 5 patients also received a pacemaker; no patient had a recurrence of syncope during follow-up. Patients who had inducible polymorphic VT and VF (n = 10) or no inducible VT (n = 18) received treatment directed at only carotid sinus syndrome. Two patients with inducible VT or VF and 1 patient without inducible VT had recurrent syncope during follow-up, but none had cardiac arrest or died suddenly.(ABSTRACT TRUNCATED AT 250 WORDS)