The purpose of the study was to define heart rate and blood pressure responses to supine and upright carotid sinus massage in healthy elderly subjects and thus to establish the validity of current diagnostic criteria for carotid sinus syndrome in this age group. Twenty-five healthy asymptomatic subjects (61-87 years) had carotid sinus massage carried out following a standardized technique employing previously defined criteria for abnormal heart rate and blood pressure responses: 3 s asystole and a 50 mmHg fall in systolic blood pressure independent of any heart rate slowing (after intravenous atropine). No cardioinhibitory responses of greater than 3 s were documented. The mean maximal cardioinhibitory response was 1038 +/- 195 msec. Right-sided responses were more marked than left when upright (1040 +/- 202 vs. 946 +/- 135 msec; p < 0.01) but not when supine (1094 +/- 215 vs. 1073 +/- 194 msec; NS). After atropine three subjects (12%) had a significant vasodepressor response when upright, but none when supine. The mean maximal vasodepressor response was 21 +/- 14 mmHg. Right-sided blood pressure responses were more marked than left (p < 0.01). There was no fixed relationship between maximum heart rate slowing and the degree of vasodepression during massage (range 2-80 msec/mmHg). The diagnostic criteria for heart rate and blood pressure responses in carotid sinus syndrome are appropriate for supine carotid sinus massage in elderly subjects. Asymptomatic vasodepressor responses occur in a small proportion of healthy elderly when upright.